Sounds like the auto-adjuster has not taken up the slack from the new install. Have someone listen for the adjusters clicking while you push down on the brake peddle. If they are clicking, keep pumping the brakes until it stops. May be many times if you installed them loose. If they are not clicking, you'll have to open it up to see why the auto-adjuster is not engaging - don't know if they'll work if there is too most slack to begin with.
This assumes you didn't open up the hydraulics, you'll probably also need to bleed the system if you did that.