I'm using 10.9.5 and I don't know how to find how much space I have

[galaksy]

Also I would like to locate exactly which files are taking up how much space...

 

[Zerka]

Click the Apple, System Preferences, the Storage. Or click the Apple, click About, and there should be a "Storage" tab on the top. To find out what folders are taking up the most space I like to use an app called Disk Inventory X

http://www.derlien.com/downloads/index.html

 

[tevion5]

I can't recommend Disk Utility X enough. It's brilliant.

 

[Alimar]

Also I would like to locate exactly which files are taking up how much space...

Go to: View > Show Status, and the disk info will show at the bottom of each open finder window.

 

[galaksy]

I downloaded Disk Inventory X but it says "You can’t open the application “Disk Inventory X” because PowerPC applications are no longer supported."

 

[DeltaMac]

I downloaded Disk Inventory X but it says "You can’t open the application “Disk Inventory X” because PowerPC applications are no longer supported."

You would download from that linked page:
http://www.derlien.com/downloads/index.html

Choose the top-most download on that page.