Assuming that it came with all of the parts, it just needs a receiver and building tools. Sometimes the parts are missing things, like the locking shoulder, for example, although even if it has one you may need to get a different one.
Best receiver is an IMBEL, obviously, for a build on an IMBEL Type 3 kit (unless you have one of the few Type 2 kits). I think Pars still has them available and you can find them on sites like the FAL Files.
Build tools can include the receiver wrench, cheater bar for leverage, bench vise, vise blocks for the barrel, buttstock tool, bolt disassembly tool, headspace gauges, and pin or rod guages to determine locking shoulder size (FN used rods, but these are uncommon; pin gauges are usually used). You'll also need timing rods or some other way to ensure proper alignment. Hammer and punches will also be of use, as well as a few sizes of screwdriver. Mark Graham's guide can be handy to have if you're unsure of anything or want some more technical knowledge.
If there are any issues with the parts or the way they come together (like the barrel not timing within the ideal range when installed by hand only), and you don't have the tools, machinery, skills, and expertise to fix the problems, the best bet is to go to one of the expert FAL gunsmiths like Mark Graham, Terry Bridwell, Randy Kline, et al.
It should be noted that FN headspauce gauges are sized differently than commercial American ones.
I don't even concern myself with 922r anymore.