Startup disc full

I bought my Mac off a friend and once I did, I took my Macbook to an Apple store and they deleted everything off of it, wiped it clean. Now my Startup disc is very very full.

I have Finalcut and Photoshop among other Apps on my computer that I do not want to get rid of. If I put all videos, music, and photos onto an external hard drive, is there a way to wipe the computer clean without getting rid of my apps? I don't have access to my discs to load Finalcut and Photoshop again. I know there are simple ways to delete extra stuff to clear up space on the Startup disc, but if I can I'd like to just clean it all up. I also just moved to Korea so I don't have any access to a proper Apple store.

Hope to hear back, thanks!!!

 

Will check it out! Thanks for the help. But, I am still curious if I can pursue my original request? I'm keen on just saving what is important and trying to wipe the computer clean but keep my applications. I really hope this is possible??