Tryna talk to this girl in her DMs but idk what to start with

I am a 18M finished my first year of uni and since summer began thought it would be a good time to ask a girl out from high school that I had planned to do a while before. The thing is I’ve had a handful of interactions with her during our classes. We both follow each other on IG and that’s essentially where I plan to converse with her. My only problem is I don’t know how to start the convo because I don’t want to risk it being awkward. Some of my friends are telling me different things but I’d like to hear it from you guys please.