How to realize the second boundary condition (Neumann boundary) in UEL of ABAQUS

There are higher-order deformation gradients  in the  higher-order deformation theory, in which higher-order stresses are usually  involvded in order to meet conjugating principle. In that way ,higher-order stress boundary conditions (such as Neumanm boundary ) should be applied when solving the partial differential eqution.

I want to know  how to apply this second boundary in UEL of ABAQUS. 

any help and suggestions are greatly appreciated.