If you want to play ACNL on Pretendo servers, you just need to update to the latest version. Once you’ve done that, launch Nimbus and you should be asked to reboot your console. Then, every time you want to play ACNL, just go into Nimbus and activate the plugin loader and then launch ACNL.
To find friends, there’s a dedicated ACNL friend code exchange at Friend Code Exchange for Animal Crossing: New Leaf