You need to open another terminal on the first server, or run the multichaind on the first server in daemon mode with multichaind -daemon, then either type multichain-cli chain1 grant 1.. connect or launch multichain-cli, and then type grant 1.. connect, in it.
Don't forget to replace the 1.. part with the address of the second server, which is shown when you launch it with the multichaind chain1@[ip-address]:[port], command.
Once that is done, re lauch the second server's multichaind process, and it should go smoothly.