First of all your gonna need to download a Clean Patch or Teh1337's example patch.
Teh1337's example patch:http://www.mptc.gov.kh/FileUpload/examplepatchteh1337.zip

2nd:Your gonna go to cod4.thetechgame.com for the online app!

3rd:Now your gonna go to were it says "ADD NEW MENU" and type in the box below it "MAIN MENU"

4th: Now your gonna add all your menu's such as Visions Menu, Messages Menu, Infections Menu,Before your done adding your menus make sure u added a R2R MENU etc..

5th: Now start doing your Menu's, Open your menu off choice, and in the box were it says "Option" Type what u want the mod to say in your Menu. Then go to the box were it says "Function" type the codes that it takes to do the mod u picked.
FOR EXAMPLE Option:Toggle Lasersight |Function: toggle laserForceOn 1 0;

6th: After your Menu's are completed, open the R2R Menu and for the first Option type something like "Give Instructions" Then for the Function type "scr_do_notify ^6WALK FORWARD NOW!!!;

7th: For the other option type "Start Infection!, for the function type "vstr startit"
Make another Option that says "Give Handler",and the function is "setfromdvar ui_mapname maplol;setfromdvar ui_gametype gamelol"-JUST COPY AND PASTE THAT!

8th: You should be finished with all your menu's accept MAIN MENU. Open that, now add enough options for all the menu's u made including the main menu. For th options type the name of the menu EXACTLY THE WAY YOU NAMED THEM and do that to all the options. Now for the functions go over and click the arrow in the box next to function and choose the name of the menu that u made for the option.

9th: After your done with that Click "Generate Menu" and u should get a box that says GSC Script. Copy and paste everything in that box! Open the patch u downloaded earlier in .FF Viewer and go to the second tab i think? It says maps/mp/gametypes/itscarter. Delete everything in that and paste the GSC Script you copied from the menu you just made. Now just save the fastfile and your done!