Replying to Help with a lock in my house

i have this lock in my house, and a key i know that matches with it. the only problem is that it wont unlock! its a safe that looks like a file cabinet, and need to grab my bank book to get some $$ for something without my parents knowing it was me.

the safe looks like a file cabinet, except much more secure. the lock is kinda upside down, so where the top of the key would be normally, it is on the bottom. the lock is made by "Chicago Locks" if it matters.

when i try to unlock it, it just wont turn. any tips to getting it to turn?