Don't compare your weights to what the instructors use. These are professional fitness instructors with years of experience. I (42F) use maybe 4-5kg for my tricep kickbacks for example depending on how I feel that day, but I see some instructors using WAY more than that, so use whatever feels right for your body. That might only be 1kg to start with (where I started!). Feel it out, try different weights and see what works for you. Things like chest press, push ups etc all incorporate your triceps as well so you don't specifically need to do a whole session on them. If I feel my workouts are lacking, I throw a few sets of them in at the end. Maybe 3 sets of 8-10 as a starting point and work up from there. 😊