Most of the Admin features are available for TFS 2015 through the Browser Console. These can be managed using the URL:

http://servername:8080/tfs/_admin

If you need to create a new Team Project under an existing Collection, you need to be part of the Project Collection Administrators Group for that collection in TFS 2015.

The URL to access that is :

http://servername:8080/tfs/collectionname/_admin/_security/?_a=members

You can add Windows user or group or TFS group.

To create a New Team Project, go to the following URL:

http://servername:8080/tfs/collectionname/_admin

and click on New Team Project and fill out the required details and click on Create Project.

This will reflect in the Source Control Explorer in Visual Studio where you can then start creating branches.