|First off, do the obvious: download the app from the App Store or Android Market. Simply search for 'Steam' and install the one that's marked as published by 'Valve Corporation'.|
You'll know if you've grabbed the right thing by the screenshots that are supplied.
Make sure you grab the right app - there are a few dodgy fakes out there!
|As soon as you run the app, it'll ask you for your Steam username and password. If you have Steam Guard running on your account, the app will then ask you to verify your account by inputting a code that will be sent to your email address.|
Once you've done this, the app will then let you know that you can't access the app yet, but that you've been entered to receive beta access.
|Now, it's time to visit your PC Steam client! It won't happen instantly, but give it a few hours, and you should find a present waiting for you in the 'Gifts' section of the PC client.|
To gain access to this section, go to the top menu in the Steam PC client and click 'Games'. Then, click 'Manage Gifts and Guest Passes' in the drop-down menu.
|If you've received a code for the Steam Mobile beta, you should find it in here with the rest of your gifts. Click on it and then enter the code given on the right-hand side of the Steam client into your Steam Mobile app to unlock the beta.|
If you haven't yet received it, don't despair - just wait a little while longer. It has been known to take anything from a couple of hours to a day to come through.