Most simple (but certainly not most effective) thing is to create different users on the machine. Anything else requires additional parameters in the CLI.
If you can't figure that out from -h then it's safer to not try it. Better wait for the GUI wallet or create two users on your machine. Or create VMs if you don't like switching users on the bare metal OS.
To do this, set the following parameters on the command line or, better, in a config file (`--configfile`). rpclisten - Both wallets can't listen on the same port. At least one must specify a nonstandard port. datadir - where they put their wallet.db and RPC cert+key