Quick Guide For Playing Agar.io With Friends! > Join The Same Server!
Steps for scout/first person
1.Have someone join a server and press F12.
2.At the top of the window that opens (at the bottom of the browser) select "Console" the far right option.
3.It should say "Connecting to: IP ADDRESS: PORT)"
4.Send this ip address and port to your friends
Steps for friends joining
1.Open agar.io and press F12
2.Go to the console
3. Get the ip address + port from your scout friend
3.Type in (in the textbox of 'console' section where the > is): connect("ws://x.x.x.x/x")
Your now in the same server

Have fun and don't get eaten!