So first before we start:
You will need a copy of Star Wars Battlefront 2 Mod Tools (available here: https://www.moddb.com/games/star-wars-battlefront-ii/downloads/star-wars-battlefront-ii-mod-tools-pc)
also if you are using windows 7 or later you will need the fixed and improved munge files (install instructions and files found here: http://www.gametoast.com/viewtopic.php?f=64&t=30415)
Now navigate to C:\BF2_ModTools\data_BUILD (or wherever you mod folder is) and open up ModTools_visualmunge.exe if it prompts you to select your battlefront folder do so.
NOW: CREATE A TESTING WORLD. I cannot stress this enough, a testing world should be where you put all your object while you are making and debugging your models, your models should be removed from the testing world when done, this speeds up the munging process especially if you are only debugging your one model. under your 3 letter name type in anything you will also need to add a world name and a description. when complete click Create world. below is a picture of my template used for my testing world. (note select your game modes, i usually only select conquest for my testing world)

Once your world is created navigate to your worlds folder (in this example mine is C:\BF2_ModTools\data_T5T).
first we want to set up our world to make sure we can debug everything for our models. so right click ZeroEditor and Click Run As Administrator. Once in Zero editor click Load in the top left hand corner then navigate to your maps world folder and open the .wld file (in my case it would be found at C:\BF2_ModTools\data_T5T\Worlds\T5T\world1)

when the prompt pops up to pick your layers click select all in the lower left hand corner.

Next we are going to set a world light to debug our current object and all future objects. go into the lighting tab on the far right of zero editor (green box in screen shot below)

First once in the lighting tab click place (blue box) we will want this to be a directional light (to test shadows later on) so click DIR (yellow box), then click cast shadows (green box) finally we also will want to be able to properly debug specular (red box). Finally you click on the map to place the light where you want.

Once your light is placed click select (green box) and select your light (you can hold down the “X” key to rotate your light and use the right / left / middle mouse buttons to rotate it, i recommend rotating it slightly down and to either the left or right to properly debug lighting effects)
in the Name box (yellow box, type dirlight) then in the far right corner where it says directional light 1 type dirlight again. This will assign this light as the worlds primary directional light. Finally once your light is in place click Save (blue box) and overwrite your old world file.

Next navigate to your C:\BF2_ModTools\data_T5T\Worlds\T5T folder and create two new folder names msh and odf. your folder should look like above. Inside of the msh folder place any texture you apply to your model (you should do this before you apply a texture to a model in xsi so you can keep editing the texture from this folder, but if youve already applied a texture the game engine will still read it.)

Back in XSI create a null (Model > primitives > null) or on the mainshelf it is the red box highlighted above. After this is created press the “8” key to open the explorer.

In the XSI explorer right click your null and rename it DummyRoot, then drag and drop every object you want to export into that null (in this case i just drag and drop cube) press the “+” sign next to the null to make sure your objects made it in alright (for me it looks like this)

Finally select dummy root and go to the top menu of XSI and go ZE Tools > export .msh.

When the exporter pops up click the “…” and navigate to your test worlds newly created msh folder, name the object whatever you like, above is what my directory was set to. once that is done just click export.
Next navigate to your odf folder and create a new notepad document name it whatever you like but change the extension from .txt to .odf
in this case i made a file called testcube.odf, open this file and type what you see in the image below (replacing the word testcube.msh with whatever you named the object you exported from xsi)


Back in zero editor go into object mode (green box), click place (blue box) and where it says odf file click browse (red box). navigate to your odf folder and click the odf you created, once loaded simply place your object (you can use x to rotate your object after its place if you select it, and use c to change your objects position if needed). Once your object is placed save your world.
Next navigate to your maps _build folder (for me its C:\BF2_ModTools\data_T5T_BUILD)
in there click Mod Tools_visualmunge.exe
once open make sure your world is selected and then simply click munge, once a pop up shows up run SWBF2 and see your new object. (depending where you placed it you may have to search the map for a bit)