Setting up Rinkeby on MetaMask
Open MateMask and go to the tab in the top center that displays your current network. Then select this and then select Rinkeby Test Network. Now your all setup!
However If you don't see the test networks listed on your MetaMask then open the advanced settings menu and turn on show test networks. Now they will show up in the network tab and you can select Rinkeby Test Network.
Getting test Eth
You will need a small amount of test Eth to use the app. You can get this easily from the link below: