SharePoint - Site Permissions
SharePoint site permissions need to be set by one of the site owners.
Instructions
Navigate to the SharePoint site.
Select the icon in the top-right, then select Advanced permissions settings.
Choose the group with the level of permission you would like to grant. Select the visitors group to grant read-only permissions.
Select New → Add Users.
Enter the user name(s) then select Share.
Highlight important information in a panel like this one. To edit this panel's color or style, select one of the options in the menu.