Alt+f3? That does nothing for me, but I'll guess you meant remotes...
Code:
on *:START:{
  server irc.server1.com -j #a,#b,#c
  server -m irc.server2.com -j #d,#e,#f
}

will join #a, #b and #c on the first server and #d, #e and #f on the second server.