On the PC version, hoppers can be connected into a loop by typing shift while right clicking, but on PE, this is not doable as everytime i try to attach hoppers together into a loop, it will bring up the UI. Hopefully there will be a new button that we can use to open hoppers, and attach hoppers and chests/ hoppers by default.
You sneak (double tap the sneak button) to attach blocks to interactive blocks.