Noob question or 2...

Hey guys. I've been lurking here for a couple of days while I atempt my first skin. but haven't seen the answers I'm looking for.
I get that you can drop and drag your .PSD into the interface folder to use/preview your skin. What I don't get is: what is a .XSF file (obviously it's an extension associated w/ Xion) ... and how do I convert my .PSD to a .XSF file type?
I'm sure I'll have some other questions....but for now, that's probably all.
Thanks in advance for any help you all can provide.
Also, while I'm posting, I'd like to say Great Job on this player. For someone like me, that likes to play w/ Photoshop making interfaces ... but NEVER wants to learn any coding, this is the most ideal player available!
I get that you can drop and drag your .PSD into the interface folder to use/preview your skin. What I don't get is: what is a .XSF file (obviously it's an extension associated w/ Xion) ... and how do I convert my .PSD to a .XSF file type?
I'm sure I'll have some other questions....but for now, that's probably all.
Thanks in advance for any help you all can provide.
Also, while I'm posting, I'd like to say Great Job on this player. For someone like me, that likes to play w/ Photoshop making interfaces ... but NEVER wants to learn any coding, this is the most ideal player available!