I would look up and read about these exercises. I have done and they should work using your set:
1) Seated overhead dumbbell triceps extension (one arm);
2) Seated overhead dumbbell triceps extension (two arm);
3) Triceps extension while kneeling on a bench ("Dumbbell Kickback").
If you can find a way to do Dips (a bench will work for this), these are also great for triceps!
I've seen that there are some videos on YouTube.
As always, keep good posture and mind your form!