Anyone can request access for other users on a SharePoint site. Simply click the Share button at the top right side of the screen. Enter the names or email addresses of the users and click the Share button. If you are a site owner, you will be able to choose the level of access, otherwise an email will be sent to the site owner for confirmation of the access request.
Atlas Email and SharePoint Online (O365)
When adding access for users with SharePoint Online (O365), please choose the user's Atlas email only. You can distinguish the Atlas email from the Valencia email by the @mail prefix.
For example: email@example.com
SharePoint uses groups to help manage the user permissions. You will be given three default groups when you start your SharePoint site: Owners, Members, and Visitors. You will need to decide who on your team will go into which group since they each have different permission levels. Owners have full control (including user management). Members have access to add/edit/delete content. Visitors can only read content. Groups make it easier to control permissions since you will not have to determine what permissions to give each user as they are added.