Going on a date for the first time?

so I met this guy on tinder and we quickly found out that we have mutual friends. In fact, very mutual. Basically he is my best friend’s boyfriend’s best friend. He asked me to go on a double date with them. I am 18 years old. It is embarrassing to admit but I’ve never been on a date and I really want to impress this guy. I said yes and my friend approves but I’m still really nervous. How do I act flirty? What should I wear? I feel like a child even though I’m 18.🤦🏽‍♀️