If a user has a link to an object such as a site, library or document, but they do not have permission to access it, they will be presented with a screen where they can request access from the owner.
The owner of the site will be notified by email and will have the option to approve or decline the request.
To set up access requests:
- Click on the settings cog in the top right corner > 'Site Contents', 'Site Settings' then 'Site Permissions'.
- If the site has unique permissions, there will be a button for 'Access Request Settings'.