SharePoint can be accessed by either going to the URL of the site or by clicking the Team Site link from the Office 365 Portal.
1. To log into SharePoint from the Office 365 Portal, go to http://portal.microsoftonline.com. Once logged in, click the Team Site link at the top. (A SharePoint license is required.)
2. If SharePoint is set up, the URL of the SharePoint site is http://SOMETHING.Sharepoint.com. The internal SharePoint site URL cannot be changed; in order to have a custom URL, a public-facing website must be set up (See Change URL of SharePoint Site). Users may bypass the Microsoft Online Portal by using the internal SharePoint site URL.