Ummm... Project64 does NOT have online complatability. It's might be added in version 1.7, though... You'd probably be best if you just wait until then, all other alternatives are very SLOW...
They were referring to PJ64k. It's based on an older version, so you'll likely encounter problems that have since been fixed. It also means that it's not officially supported here.
the main problem with pj64k (other than it is based off the pj64 1.4 core), is that it utilizes a software called kaillera for it's online capabilities. a software which hasn't seen an update in 5 years and was designed for old console emulators such as commodore 64 emulators. it wasn't designed for n64 emulators, it is too much for it. which is why you see alot of desyncronization and lag when trying to play super smash bros over the internet. I think the only games that are stable over kaillera are games which don't incorperate alot of gameplay action such as marioparty.