You can assign multiple materials inside the Details panel of the mesh. If you set up your mesh correctly, there should be multiple elements inside the Materials subheading, each corresponding to your separate UV channels.
In order to ensure that your mesh will have multiple elements for materials, make sure to set up separate materials in Maya before export. For example, set everything from UV set 1 to use lambert1 and everything from UV set 2 to use lambert2.
Here’s the window you’re looking for in Unreal.