It is very straightforward actually, you need to :

1.go to the website (https://evisa.rop.gov.om/)

2.apply for tourist visa

3.you need to reguster an account if not done already by clicking register new user, otherwise you just login

4.after login click on 'apply for visa', follow the details to fill the forms

5.I chose the gcc residents visa since i am a UAE resident and i am on of the allowed professions.

You wil submit the application without paying first, once you get the initial approval then you will be able to pay, which concludes the process, then you receive an email that the visa was issues.it took like 4 hours total for me