How to add a timer in CapCut
Download the timer on a green background. In CapCut, drag it onto the track above your video so it sits on top as an overlay. Select it, open Video → Remove BG → Chroma key, pick the green with the color picker and raise Strength until the background is gone. Menu names move a little between CapCut versions; look for Chroma key. If you made it on black instead, set the clip's blend mode to Screen.