Wet behind the ears, what does it mean?

I'm not a 100% sure but I think it means young as in someone with no experience

You're wet when you're born. So wet behind the ears is you're still a baby who hasn't even been completely dried. So you have no experienc.

Thank you :)

lacking experince so bassically he's telling him he's still naive about kissing/love

It's an old person saying.