You could probably find some threads with forum search.
You can use gym machines or free weights, I tend towards the former for beginners; get someone to show you if possible for the free weights.
Generally, start with things like 3x10 reps or 2x20 reps with enough weight to tire your legs. At least 2 minutes between. You should see some rapid improvement in strength if you haven't done this before, then you can move to higher weight and 3x5 reps or 2x10 reps as time goes on. I wouldn't do low-weight, 100 reps as I have heard some people doing! Quads & hamstrings (carefully) are the key ones. Try and get some calf raises in too, can be done on some reclined squat machines quite nicely. Anything else you can do if/when you feel like it or for specific rehab purposes, but be sure to do some body-weight/conditioning exercises as well, to work things like the core, glutes, QLs (sides above hips. I won't say not to do sit-ups and press-ups, but there are more specific exercises for running posture, so take your pick. People usually do some upper body work, but it doesn't have to be a lot.
Nowadays, I mostly use free weights at home (when I can be bothered.. not been going too well this year!), I do a small amount on upper body, but mostly squats/lunges/Bulgarian-split-squats for legs, sometimes working with the weight overhead which adds in some core & stability. Snatches become annoying (I don't have a rack so I am perennially picking the weights up from the floor!), jerks are fun. And the body-weight stuff is just as important as working with the weights.