Believe it or not kissing is as easy as breathing,
as soon as you stop thinking, it will just happen! It's one of the most natural things in the world, humans have been doing it for millennia, it is engrained in your very genes, and you WILL do it just fine

Just as when a car is approaching you naturally jump out of the way to save your life, when you're close enough to a pretty girl, your kissing mechanism will take over!! You can actually make breathing complicated if you think about it too much. Go with the flow, look into her eyes, think about how pretty she is, and the rest will follow