Please be aware IF you launch a multiplayer session, and there is already a Host / DM present, it will automatically sync the hosts map... this will wipe your map so make sure to download the map regularly!
How to download map:dl
This will either download to your downloads folder (web) OR launch a save dialog.
How To Launch Multiplayer
.nick yourname
.join
before you join if you have been give server name, password and party name then you can set these by using the following commands:
.server servername
.pass password
.party partyname