Added Nov 13, 2010
San Francisco Ba...
Set your iron to its hottest steam setting. Place a press cloth between your fabric and the ironing board and place your fabric wrong side up on the press cloth. Put the interfacing on top, making sure that it isn't hanging out over the edge of your fabric. The side of the interfacing with the glue dots should be facing down (for finer interfacing, the rougher side should face down). Put a second press cloth between the interfacing and your iron. You want to prevent any glue from getting on your ironing board or iron, so the press cloths are important. Press, holding the iron down in one spot for ten seconds, lifting, and moving to the next spot, overlapping slightly with the previous press. Pressing is different from ironing in that you should not move the iron around as you press the interfacing. This may cause wrinkles to form in your interfacing and fabric.
For more the manufacturer's directions, see the plastic slip that is wrapped around your interfacing that you buy at the store. Keeping this plastic is also helfpul in identifying the different types of interfacing you have once you are home and they have been buried away in your stash.