not all brakes are the same. just for reference, I am doing this with SRAM force caliper brakes.
use an allen key to remove your break pad housing.
once removed, loosen the little screw that holds your break pad in.
slide the old brake pad out.
slide the new brake pad in.
re-tighten the little screw.
put that shit back on and down a mountain at 40mph to test them.