Lay down the vapor retarder on the soil in the crawlspace. Leave at least 12 inches of vapor retarder overlapping in all areas to allow you to secure it to the wall.
Start from one corner of the crawlspace. Staple the liner to the wall around 2 inches from the top with the staple gun. Use only turf staples as they secure the liner the best to the wall. Work your way around the crawlspace, stapling the liner every 6 inches.
Tape over the staples and the corners of the vapor retarder liner with the fiberglass mesh tape. This process will provide an airtight seal and not let any moisture leave via the staples.
Seal the vent. If the wall is masonry, use bricks to cover the entrance. Lay the bricks and secure them with cement. If the wall is made of wood, cover the entrance with wood siding. The most time-efficient and cost-effective way would be to buy sealed crawlspace vents. You can find or order these products at most large hardware stores.