Pound along the mortar seam with a chisel and hammer to break away the row of brick veneer along the top edge of the window. Remove excess mortar off the wall with the chisel so the installation surface is smooth.
Spread a 1/2-inch layer of mortar over the window with a trowel and attach a section of steel lintel over the window so it extends at least 4 inches past the side edges of the window. Place a level on the lintel edge to verify it is horizontally level. Drill pilot holes with a carbide drill bit through the lintel and screw it in place with installation bolts.
Hold a section of metal flashing over the top of the lintel so the protruding portion of the flashing is flush with the bottom of the lintel. Use a level to make sure it is horizontally straight. Drill pilot holes with a carbide drill bit and screw the metal flashing in place with masonry screws.
Spread about 1 inch of mortar over the flashing edge screwed to the wall, using a trowel. Press the brick veneer into the mortar so the spacing is the same as the other brick veneer on the wall. Smooth the mortar between the brick veneer with your finger.