The standard home page upon logging into the communities is to the right, but, you can make any of your custom streams your home page. Watch
If you look at the left-hand navigation there are the basic streams, activity, and connections .Under those custom streams you have made will display. In my case these are, team, mainframe, and security. All that is needed to change your home page from the standard home page to one of your choosing is to select the stream you would like to make your home page (in my case Mainframe.) Once selected you will see a gear icon to the right of the stream name, select it. Now you should see the choices, edit stream, seat as home, and delete. Set as Home is the correct choice.
Upon logging in the Communities home page will now display your custom stream instead of the standard home page.