Add Delta Time to Existing Game

My game currently moves objects without delta time and runs at different speeds on different computers.

Current movement code:
[paste your movement code, e.g., "player.x += 5"]

Help me:
1. Calculate delta time (time since last frame)
2. Convert my movement to be time-based instead of frame-based
3. Ensure physics and animations stay consistent at any frame rate

My game uses: [language/framework]
Current target FPS: [e.g., 60]

Explain what delta time is and show before/after examples so I understand the change.