
At first, just experiment with the machines! Start with low weights and get a feel for them. Focus on figuring out proper form and mind-muscle connection before focusing on lifting heavy. Do some light warmup cardio (so you don't burn through all your energy before your circuit), then heftier post-lift cardio! Some great lower body machines: hip adductor and abductors, leg press, laying or seated hamstring curls, kickback machine, leg extensions (quads), and glute-focused back extension
If your gym has a hip thrust machine, that too!! Good back machines: Lat pulldowns, chest supported rows, rear delt flies on peck deck Good upper body machines: Preacher curls and bicep curl machines (for biceps), tricep pushdown machine, chest press, peck deck (chest) Good ab machines: Ab crunch chair (both kinds, the one with your feet planted, and the one where your seated elevated), hanging leg raises
I'd say to only do machines until you get a feel for the motions and build base muscle, then you can experiment with compound lifts/cable machines/free-weights Also, focus on diet A LOT!! To get fit, what you put in your body SERIOUSLY matters. Get in very good protein and fiber on the daily, try to avoid added sugars and alcohol, and just try to consume as many good nutrients as you can on the daily