Paste this into your remotes (Press Alt+R to open the remotes editor), edit the servers and channels as needed.
Code:
on *:start:{
  server [color:blue]irc.server.net[/color] -j [color:green]#channel1,#channel2[/color]
  server -m [color:blue]irc.fnet,com[/color] -j [color:green]#anotherchan,#channel3,#chan2[/color]
  server -m [color:blue]irc2.someserver.net[/color]-j [color:green]#chan1[/color]
}