Please note that not all Greasemonkey scripts run on Opera. However, most of them works just fine 🙂
Create a folder any where in your computer. Name it as you like (exapmle: MyOperaScript).
Copy user script file on that folder.
Launch Opera. Then Go to:
select the folder created in step 1.
Click “OK” and exit preference window.
That’s so simple! 😀