Note: It's usually a very good idea to make a back-up of the track before attempting this!!
1. Open your track's SDF file in Plaything2 (assuming that all of the tracks texturing and non-car stuff has already been done)
2. Go to "TrackTools -> Carma 2 -> Pre-process Track"
3. Now, the Preprocess window should appear...
Input (The Browse-buttons in "Reg dir" and "Game Track Dir" don't work)
-Track File: choose the track's SDF
-Extra Files: leave this blank.
-Reg Dir: type in the path to your Carma2 reg directory. (e.g: "D:\Carma2\data\reg")
-Game Track Dir: type in the path to the track that you're working on. (e.g: "D:\Carma2\data\races\mytrack")
-Base Name: for this, select "browse" and pick the track's .act file.
-Calculate Smoothing groups: leave this checked.
-Generate Map: only check this if you haven't already made the in-game map for the track.
.....Generate Map's Options: .....Rotate map by ### Degrees: rotates the map file that will be generated
.....Zoom out by ### Percent: adjusts how large the generated map will be
.....Ignore Materials: Add the names of any materials that you don't want visible on the map
-Tidy Up Kerbs (Optional)
-Worry About Smash Materials: Check this only if you plan to have smashable textures in your track. Windows & fences for example.
-Set Materials: add the names of the materials you want as smashables
-Default Material: leave this blank
4. Hit OK to start the preprocessin'!
(If all went well, your track can now have pedestrians and smashables!)