Staple waterproof membrane, such as a polyethylene film, to the wood sheathing of the house. Cut out windows, doors and other openings with a utility knife. Cover all seams and edges with a matching tape.
Place the first foam board panel at a wall corner. Measure 1 inch up from the bottom of the wood sheathing all the way around the house, then snap a level chalk line to mark the bottom for the panels. Align the outside of the first panel with the wall edge using a long, straight board.
Nail the panel to the wall studs, spacing nails every 12 inches horizontally and vertically, using a hammer.
Set the next panel with the edge tight against the first panel; fit tongue and groove together if the material has that type of connection. Use a utility knife to cut small openings for pipes, outdoor electrical boxes and other elements as you go. Run foam board over wall and window openings, nailing it securely to framing around these openings. Go back with a utility knife, drywall saw or reciprocal saw and cut out these openings once all walls are sheathed in foam board.
Seal the seams between panels, over nail heads, at wall edges and corners, and at door and window openings with foam board tape. Use a type to match the foam board, of the same basic type of material and from the same manufacturer.