Hello katierose,
I've never had any useage for Crashplan, but I can share some things that might help.
I would first check "Activity Monitor" to see if Crashplan (or any of it's background processes) are running. It might be why you receive the locked error message when trying to delete it. You'll want to locate anything related to Crashplan and "End Process". Then try to search your harddrive for the files and see if you can delete it then.
Instructions are available here: View information about Mac processes in Activity Monitor - Apple Support
Activity Monitor can be launched a number of ways. The easiest is to hold the Command Button and tap the Space Bar. This launches Spotlight Search (which is actually my favorite way to load any application) and you can just start typing: Activity Monitor and hit Enter.
If that doesn't work, search the Support site for this particular program. You may be able to find an "uninstaller" which will do all the hardwork for you.
Search Support on for CrashPlan:
-> https://support.code42.com/Search?search=uninstall&fpid=41457#product=undefined&version=undefined&search=uninstall