Before any insulation project, make sure you caulk and/or seal any openings.
Due to the nature of insulation products, it is recommended that you wear protective eye glasses, a dust mask and gloves.

1. Open the insulation bags by cutting lengthwise through the side panel. Be careful to avoid cutting the product. The insulation will quickly expand to its full volume when the bag is opened.


2. Gently push batts into the cavity so that it sits all the way in, especially at the corner and edges.


3. Fluff it to its full expansion by pulling it forward to fill the depth of the cavity. The fit should be snug. Allow friction to hold the batts in place.
   For shorter spaces, cut the insulation to fit properly. Don't double it over or compress it. Compression changes the R-value of the insulation.
   Cut insulation about an inch wider than the space using a sharp utility knife against a safe backstop such as an unfinished floor or other smooth, flat surface. Use a straight edge to hold the insulation in place and guide your cut (a metal ruler or T-square for example). Always cut on the unfaced side of the batt. Cut insulation to fit snugly around obstructions such as electrical boxes and plumbing.
   If it takes more than one batt to fill the height of a wall cavity, make sure the two pieces are butted snugly together.
   
   Use scraps to fill around windows and other openings.
   
   Once all of the insulation is in place, you will need to cover it with a vapor barrier, or poly.

To prepare for application:

1. Fill in any narrow gaps between joists by forcing pieces of unfaced insulation into the gaps with a screwdriver or putty knife.


2. To control air leakage, apply caulk or foam sealants around openings like window and door frames and any openings where wires or pipes go through the exterior wall.

To apply a vapor retarder:

1. To apply the poly film, start at the top plate in one corner of the room.


2. Pull the film tight and staple at least every 12 inches.


3. Drive staples at the center of every stud and around openings, working around the room.


4. Overlap the sheets by one complete cavity to minimize leakage. Then staple evenly through, fastening both sheets to the studs at one- to two-foot intervals.


5. Pull the film tight along the sole plate and staple in the same manner, making sure the staples are driven flat, flush to the stud surface.


6. Trim out the poly from over windows, doors and electrical boxes.

Note: In areas of the country where vapor retarders are not required, bathrooms would require unfaced insulation and no poly film covering to allow moisture to escape.
Check out this link to Owens Corning website for detialed How To Videos: http://insulation.owenscorning.com/homeowners/tools-resources/videos.aspx