Please help with treatment of teen who had mouth trauma?

Not a computer? That is a question for the office or er if the injury is severe. If you don't have an ENT or facial plastic surgeon, go to your pcp. If there are deep lacerations, they will need to be cleaned at closed. Antibiotics may be prescribed. The teeth and jawbones need to be evaluated as well, x-rays could be indicated. If there is significant dental or bony injury, surgery might be recommended.
How? Where? What injur. This is a broad question."trauma" includes lceration, fracture, burns (thermal or electrical) and so forth. So, you can see the treatment is directed towards the specific trauma. Can you be little mor specific?
Need more details. There are many different injuries that can happen with "mouth trauma." is this a question about a laceration to the lips or skin around the lips that should be seen and repaired within the first 6-8 hours after injury? Are there teeth involved, chipped or knocked out? Do the teeth no longer line up or does the jaw not open properly? You may need to go to the er or call your dentist.
Assess injury first. First complete an assessment of the injury. This may require radiologic evaluation to determine dental or boney injury. Soft tissue injury should be repaired if necessary as determined by a physician.