You can see that for each point you can edit X Y Z and Pitch, Heading and Roll.
Another option is to open the aiw file with a text editor, and find the [PITS] section. For each team there are two GarPos and GarOri values, and it looks like the first number is 0 for driver 1 and 1 for driver 2.
Bear in mind that if you make any further changes to the AIW from BTB, those rotations will be lost when you export. You should probably use BTB to set the general positions of things and from then on use the AIW editor for fine tuning and any other changes.