I recently got a surgery for a trimalleolar ankle fracture as well as open reduction of the syndesmosis with a screw. my orthopedic surgeon recommends non-weight bearing for 12 full weeks. when is it recommended to start putting weight on my ankle?

Listen to your surgeon. They will know the best recommendation for you. You are very young with a lot of use you want this to be perfect. You had a major injury followed with surgery. Unless you have extenuating circumstances that require a different consideration follow your surgeon’s recommendation. You can always get a second opinion with history and X-rays

Non-weight bearing for 12 weeks means do not put any weight on that ankle for 12 weeks. This typically means no weight whatsoever, not even for a second or two whether standing or seated.