this is basicly a copy and past of Elbedhar's guide to thanks to him and view original here
https://www.reddit.com/r/smashbros/comments/ifzgv/ysk_how_to_play_super_smash_bros_and_other_n64/Get the project64k emulator. Make sure it is project64k, not project64.
Get the Super Smash Bros. ROM, or the ROM of any other game you want to play online. You're on your own for finding this but chances are you already know how. If not, ask a friend or look on google.
[Optional] Get a kaillera client. The project64k download already comes with one (kailleraclient.dll). Different versions have different features, so if you ever want to change to another one, put it in your project64k folder and call it kailleraclient.dll. You can get a really good one, with p2p functionality (for less lag), here:
http://www.smashboards.com/showthread.php?t=275895Configure project64k. Go to file -> Choose ROM directory and pick the folder that you save your games in so pj64k can locate your games. Configure controls and audio / video settings in the Options menu. DO NOT use full screen for online play! Make sure you can get the game working fine OFFLINE before attempting to play online.
[Optional] I'm able to play with the keyboard just fine for most games, but if you have trouble with that, you should set up a controller. If you use a controller, go to Options -> Configure and pick the N-Rage input plugin. For Xbox 360 controllers, you can just plug in with a USB. if you want to use the actual N64 controller, look for the Mayflash USB adapter on Amazon. It's something like $15 and works fine for me. You can use Playstation controllers too but I don't have experience with them.
To actually get online, go to File -> Start Netplay. Type in a username and then search for servers in the master list or enter an IP manually. The primary IP for Smash 64 players is 69.172.242.150:27888. Another good server is GodWeapon (72.5.86.115:27888). Europe and other regions (South America, Australia, Japan, etc.) have their own servers that you may have to look for on the master list. Europe also has an MSN group for finding players:
http://www.smashboards.com/showthread.php?t=271733