Click on Gear Button -> Setup -> User -> Permission Sets. You will see 4 Options:

Address Verification (Admin) for admins needing to administer the app, Address Verification (User) - for all other users, and the two others are for Guest (running on sites) or Community users. To assign a permission set, select one of these four permission sets, then click on Manage Assignments. --> Click on Add Assignment. --> Add the user you want to give access to the Address Verification app. Save the Setting. (You can also set up a flow that automatically gives the permission set to a user on creation.)

Address Verification

Address Verification instantly cleans, verifies, and geocodes Salesforce addresses. It works with any object, supports international lookups, and features easy address auto-complete.