Before Manifest V3 it was easy to do that, but after that bring minor change where users have more control over these kinds of permissions, which can modify the user-side page, so now you must follow a few instructions.

• Get Extension (Chrome)
• Go into Extension Manager by visiting (chrome://extensions/)
• Click on Details Button of the "Tampermonkey" extension.
• Scroll down to Allow User Scripts enable it

Start-to-end video instructions