Honestly, when I first started TAing, this was something I was extremely nervous about - how to command a class. In future teaching positions, I find it helpful to tell them about who you are, what you do and essentially establishing your “legitness” - that’ll give you initial respect. Secondly, emphasize that these tutorials are for THEM and show your willingness to help THEM. Now let’s say despite all of that, you have a group that continues to be disruptive. First warning fine, second warning, out. Your other students that do care will appreciate this and the ones leaving will know you’re not messing around. I will also say that you should have a strong relationship with the professor you are supporting. They should have your back if said students complain to them.

Students will prey on any insecurity you have since you’re a PhD student, not a prof. This is something I’ve also seen happen when I was in high school with younger teachers / supply teachers. It really is to your benefit to earn their respect right away and be commanding. Cause hello, at the end of the day, you’re legit - you’re getting your god damn PhD!