Well, first of all, in the DLL code, check the map name and techtree name to be sure that they are correct. (The map name should be the filename of a working mapfile. If you're making a colony game, the techtree should be "MULTITEK.TXT").
Next, go to the DescBlock, you'll probably see something like MultiLastOneStanding. Change this to Colony (capitalization is important). This part simply tells the game what type of mission yours is.
Now go to compile. You should get a DLL named OP2Script.dll. Copy this to your OP2 folder (along with the .map file) and rename it so it starts with a 'c' (for colony game). Also, the filename (not including .dll) has a max of 7 chars (including the 'c'). Now start op2 and your map should be listed.
OP2 will only list missions in the colony games which meet the following two conditions:
1. The filename starts with a 'c'.
2. The mission type in the DescBlock is set to Colony.
As for AI, you'll probably want to learn at least basic C++ to get started with this. There is no 'default' AI that you can add to your mission like most other games have. (OP2 doesn't have a real AI, any AI has to be part of the mission code).
Hope this helps!