Setup Site Collection Admins
Site Collection Admins have full control over every site in the Site Collection. If a user is added to the Site Collection Admins group, these permissions will override any site level permissions. The Site Collection Admins basically run the entire Site Collection. You can create multiple Site Collections, and also have different Site Collection Admins for each of the Site Collections. Below will show you how to add a user to the Site Collection Admins group.
Step 1
When you first login, click the "Admin" tab on the top,right toolbar,, use the drop down and choose SharePoint
Step 2
This will take you to the SharePoint Admin Center. Here you want to click on "Site Collections"
Step 3
On the right side of your screen, you will see all your site collection URL's. You need to put a check in the box on the main one (http://XXX.sharepoint.com) and click "Owners" in the top tool bar, then click Manage Administrators.
Step 4
A window will pop open, here you want to set your Primary Site Collection Admin, and Site Collection Admin. You can only have 1 Primary, but you can have multiple Site Collection Admins. Click OK when finished.