Add it, mount it as /home2, change DirectAdmin template files to write new domains to /home2.
I thought there was information in the knowledgebase, but I couldn't find any.
Search these forums for home2 and you'll probably find some good instructions.
Why did you put the symbol after your OS? Don't you like it? If you'd rather use something else then this might be the best time to backup, fully restore the OS with two drives (putting /home on the second drive, or using RAID0 on /home) and then reinstall DirectAdmin and then restore the users.
Note that this is NOT a recommendation that you do the latter; if you break anything or lose all your data and/or clients, it's not my fault.
Or, as we say here after some earthquakes, it's not even San Andreas' fault.