Download the bloc42 file from the FP website, find the bz2 file, extract it to your maps folder in gmod, it should be about 60,000 KB and should be a BSP not a BZ2, then launch gmod you should be good

Download the bloc42 file from the FP website, find the bz2 file, extract it to your maps folder in gmod, it should be about 60,000 KB and should be a BSP not a BZ2, then launch gmod you should be good