You're going to need to download MPASM. PBP manual states how to use MPASM assembler within the command line... example...

PBP -p16F88 myfile -ampasm

You must assign a path from your PBP directory to the one with MPASM in it.

If you have problems, you can invoke MPASM directly and load the file for assembly into the dialogue box appropriately.

Look at the 16F88.INC file for a clue as to how to embed MPASM style defines into your program - they have to be done as one contiguous line per Config word.