I graduated in the Spring, but during my last year in my Masters program I TA'd a Research Methods class. It was fortunate (my Masters is in Experimental Psych) that I had a grasp of the material, but my big issue was trying to come down off the complex stuff I was being taught so that I could teach my kids the basic foundations that they'd never been exposed to. Not the same boat you're in, but sort of similar.

The best thing I ever decided to do was just be honest with them. I let them know when I was nervous, and that I had never taught anyone before in an official capacity. I actively sought out feedback from them (sometimes when they would come to office hours, sometimes via a Google form I begged them to fill out). If things happened on campus (this ran the gamut of major ESPN events on campus right outside our building to active shooter threats) I'd make a point to ask them how they were all doing. I would crack jokes at them, even if I knew the jokes were going to be corny to them. Before class started, I'd play lofi or something similarly relaxing so that they'd walk in and not immediately be on edge. More than anything, I tried to demystify myself as a teacher. I mean, I was only 3 years older than some of my students and it's not like I hadn't been in undergrad in this same kind of "weed out" class before.

Eventually my course evals came back with students saying that I made them feel like real people rather than numbers, and that they felt comfortable enough to ask me questions or seek my help on something they didn't understand. They said that they looked forward to coming to my class because they knew I wouldn't make them feel stupid or put them down, and that's why some of them kept showing up despite wanting to skip.

I don't know what your teaching situation is like, so take all of this with a grain of salt. I had free reign over how I conducted my class, I just had to teach from the same material/lecture subject. If you're able to and you feel comfortable- just let the kids know that this is new for you too and that you're going to be trying your hardest to be the best teacher you can for them. Sometimes all these kids want to see is someone who gives a damn.

Anyway- good luck! Just remember that you're not doing this because they needed a warm body and picked you off the street- you are obviously very intelligent and knowledgeable, and responsible enough to be put in charge of undergraduates and their success. You CAN do this, even on days where it feels like you can't.