"French" kissing??

Abbs
So, despite being completely informed about sex, dating, flirting, sexualty, ect, I'm still quite uncomfortable with the idea of tongue kissing, or "French" kissing.
I'm 15 and am interested in a guy, but, if we progressed to make-outs... That's just what I don't understand. I don't understand what is appealing about it, yet I do? I also just don't understand how to master tongue kissing without having someone to practice with and be patient with.
Then again, both of us have never had partners, so we're most likely going to be both horrible. 
Do you have any tips?