How to trim a TikTok video from your phone library
1. Open the TikTok app and tap the plus icon in the bottom-center of the screen.
2. Tap "Upload" in the bottom-right, find and tap the video you want to add from your phone, and then tap "Next."
3. Use the red sliders at the bottom of the screen to change the start and end time of the clip, then hit "Next."
4. Add any effects or music you want, then post or save the video to your drafts.