How to Create a Site Collection in SharePoint Online
Open your web browser.
Navigate to the login page for the Office 365 Administration interface.
On the administration page, click the Admin drop-down list in the upper-right corner of the page.
On the SharePoint administration page, click the New button.
Select Private Site Collection from the drop-down list.
Fill in the form with the information for your Site Collection.
Click your new Site Collection.
You can view its web address and other information.
Enter the website address in a new browser window.
You can now access your new Site Collection in SharePoint Online.