You can download the app, which is available for free, at iTunes. Liefeld announced it via Twitter, and the tweet embedded below has a link to get the app.
Asked by a fan, Liefeld responded that an Android version fo the app will be available within weeks.
So I have an app. It's FREE with lots of art, video archived and you can send me questions https://t.co/0K7SclAhBR— robertliefeld (@robertliefeld) August 14, 2014
It will be "a few days" before the Liefeld App is available in the European app store.
Liefeld revealed that the app was apparently conceived at WonderCon and then developed by Curtiss Pope. It includes a free, digital copy of RE:GEX #0 from Liefeld, Jeph Loeb and Tom Mason.