CrashPlan is found on your computer in the Applications folder.
When you launch CrashPlan it will bring you to it's Backup tab first. And it may look similar to this.
Click the Restore tab.
The first blue link "most recent" when clicked will bring up a calendar where you can select the date and time to go back to try to find the file you want restored. The second blue link is "original permissions", this one can be left alone. The next is "Desktop". Clicking that once will switch to "original location" or clicking it again switches it to "a folder" where you can then select the location to restore to. The fourth blue link is "rename". Clicking it will switch to overwrite. If the file exists in the location it's restored to, it will rename the original or overwrite it.
Once you've set the date back to restore from, click through the hierarchy to find the file or files you want restored and click the box to select it.
Click the restore button and CrashPlan will restore the file to the location desired.