what do you mean?
If you don't know how just say so.... under the terrain editor look at the part of the screen where you see increase 1, 2 and decrease 1, 2 and that level one you should see one thats a ramp looking one. click on that and click and drag over the part of the cliff you want a ramp to be. (ramps must be 1 level apart not 2) or use the ramps under doodads. (those ramps are for 2 level difference)