Once you're done with the CrashPlan configuration, you can close the CrashPlan app, and the Terminal.
===Using a local CrashPlan client===
You can follow the instructions on the CrashPlan wiki on [http://support.crashplan.com/doku.php/how_to/configure_a_headless_client how to connect to a headless CrashPlan install].
It requires you to install CrashPlan on your client computer, manually editing a config file, and using SSH port forwarding.