Drive is full

Hello there! I’m having a bit of trouble with my drive - its a passport essential 500 GB, and the software says the drive is full. Does it get filled up that easy or is there a setting I should have activated? And what do I do now in getting rid of some of the excess in trying to conserve space on the drive?

If you loaded it with movies or system images it will fill up fast. If you using some kind of automatic backup it may be the problem.

Joe