Remove the bedding and sheets from the mattress.
Unroll the foam mattress pad on top of the mattress so the long edges of the pad align with the long edges of the bed.
Line up the edges of the foam mattress pad with the edges of the mattress. If your pad has an elastic skirt attached, pull the fabric over the sides of the mattress so the pad fits snugly.
Put your fitted sheet over the mattress pad and the mattress, and then make your bed as you usually do with sheets and blankets.