You'd have to rewrite the app. When the developer writes an app, they tell the app what it should need permissions for. When you run it the first time, it will prompt for those permissions but only the ones the developer decided it needed.
If you're asking how to change those permissions once you've answered the first-run prompts, there is a way. Go into Settings, apps and permissions (on a Pixel, you don't say what device you have so look for something close), find the app, tap it then tap permissions. You can modify those there.