At my gym we have two types of machines for hamstring curls. On one of the machines you lay on your stomach. With your legs straight there is a padded bar that is over your ankles, You do the curls by bending your legs at the knee and pull them back as far as you can. A good plan when starting out is very light weight and higher repetitions. I would start with an easy weight and do two sets of about 15 reps.
The other machine is similar except you do the curls from a seated position.
And if you have cable set-ups available, another way is to attach a cable to your ankles and pull each leg up one at a time while standing and facing the machine.