For a ramp, just create a cube the same dimensions of yoursteps and weld the top corners to the top of the stairs, and the bottom to the bottom of the stairs...
I'll make a quick example...

The dark grey lines are the stairs viewed from the side, the white lines are my ramp (though it should really extend to the ground plane).
I just created a cube the same size as the stairs, then moved the edges to meet the tops of the lop and bottom stair, if that makes sense.
I'll make a quick example...

The dark grey lines are the stairs viewed from the side, the white lines are my ramp (though it should really extend to the ground plane).
I just created a cube the same size as the stairs, then moved the edges to meet the tops of the lop and bottom stair, if that makes sense.