The end-user can login to the SharePoint site via the Control Panel login of the reseller and then click on the SharePoint tile.
Creation of new document
To start creating a new document the user can simply click on the appropriate tile, associated with that application, enter the name of the document and the document will be opened directly in the browser and saved in the cloud.
Configure the OneDrive Business client
If you need the URL in order to configure the OneDrive Business client you can login as an administrator into the CP, click on the SharePoint tile, Click on the "SharePoint 2013" tab, and then on "general". The Url for the drive is shown on the bottom. See below.