Simply use an extension like tampermonkey or violentmonkey or whatever monkey you like and install whichever userscript you want :)

Firefox and Chrome with Tampermonkey or Violentmonkey.

If you want, you can also check out my Greasyfork Profile, that's where I usually update my userscripts first:

https://greasyfork.org/en/users/187317-funkyjustin