All you have to do is add the Bent Normal output node to the Material Graph and then plug your Bent Normal map into it. You can find it by searching for it in the pallet. You should also make sure that you have something input into your Ambient Occlusion (AO) and Normal map input on your Material. The following image shows exactly how this should be set up
Yes, you still need Normal maps and AO maps when using Bent Normals.
This should happen when you plug your AO map into the Ambient Occlusion input like in the following image.
Make sure you are using Substance Designer 6 and should be able to bake this just like any other map. You can also read more about how to do this on the following page.
https://support.allegorithmic.com/documentation/display/SD46/Bakers