Blend

To apply a blendshape, select the target shapes first, then the destination mesh, and create the blendshape deformer as you normally would in Maya.

Once the blendshape is set up, save this information into the template
by selecting the mesh that carries the blendshape and following the save procedure described in the Overview section.

Connection to the rig

If you want animators to drive specific blendshape weights directly in the rig, you have to expose these weights through modifiers with corresponding hooks. Detailed informations in the technical references.