Nervous about being set up with someone by a friend

As a 17 year gay guy who's been in the closet up until this year (and still somewhat in the closet), I've never had any real experience with dating or relationships. However recently to my surprise, I got news that my friend wants to set me up with a friends brother who is also gay. From what I've heard, they think that i'm "cute" and my friend asked me if wouldn't mind having something set up so I can meet them. I've seen how he looks like so I was on board and after initial surprise I agreed. However now I am super nervous about meeting them. I've never been too confident and I always been very shy so I don't want to mess up a first impression but at the same time I don't want to be someone i'm not. Nothing official has been put in motion, but my friend is proposing a double date or something along the lines of that which i guess would be good for breaking the ice but never less, I still have zero dating experience and my friend who is setting me up is relatively new anyways. Hundreds of what if's are rushing through my head and I'm scared i'll fuck up bad in some way. Anyone have any advice on what to? What not today? How to handle or go about this?