Get some friends to watch it with you. The more the better. Serve fresh fruit and tea with a box of tissues.
Take breaks. Watch 20 minutes at a time. In your ten minute break, take some breaths, get a drink, talk about it with your guests. Cry if you need to.
Have someone's hand to hold or squeeze.
Look away if you need to and just listen instead.
Know that watching the film is empowering you with knowledge to act. Know that just bearing witness to their suffering is acknowleging their existence and their pain.