The easiest way to give your users access to Record Validation is with the RV Permission Set. The advantage of using the Permission Set is that it is updated automatically whenever new classes, tabs etc are added to RV. This means you don't have to make any changes after future updates where new classes might be introduced. 

However, with the RV Permission Set users have access to all of Record Validation, including the settings in RV Setup. If you don't want your users to access certain RV pages, such as RV Setup or RV Job, make sure to deny them access to those pages. 

Alternatively, you can grant your users user access via profile settings‍ or a custom permission set instead. Note that profile settings and custom permission sets need to be updated manually whenever a new class, tab etc. is added to Record Validation.

Grant access with the RV Permission Set

To grant users access to all of Record Validation:

1. Go to Salesforce Setup > Users > Permission Sets.
2. Click the Record Validation Permissions permission set.
3. At the top, click Manage Assignments.
4. Click Add Assignments.
5. Select the users you want to assign the permission set to.
6. Click Assign.

You have now granted full access to Record Validation, including all classes for current and future RV releases, to the selected users.

To deny access to certain RV pages:

1. Go to Salesforce Setup > Users > Profiles.
2. Find the profile you want to edit.
3. On the profile, go to Object Settings.
4. Find the RV tabs you want to hide and edit. 
5. Under Tab Settings, select Tab Hidden.
6. Click Save.