The latest version of the Triggertrap Mobile app needs iOS 7.0 or newer. But don't worry! You can still install the old version, which is compatible with iOS 6.
1) Without your iOS device connected, go to your computer (not on your iPhone/iPad/iPod Touch) and load http://tri.gg/ttm
2) Open the App Store, go to Updates, and click on Purchases.
3) Click on the button that says "Free" and let it download.
4) On your iPhone/iPad/iPod Touch, open "App Store".
5) Click on "Purchased" in the bottom menu.
6) Click on "Not on this device" in the top bar, then "iPhone" below it.
7) You should see the Triggertrap icon. Click the cloud button next to it.
It should ask if you want to install an older version. Agree to this.