The first instruction outranks this page: your surgeon told you how to care for it, and that comes first. What follows is a reminder, not a replacement.
What the dressing is for. Dressings protect your wound from germs, reduce the risk of infection, cover the wound so that stitches or staples do not catch on clothing, protect the area as it heals, and soak up any fluids that leak from the wound.
How long to leave it. You can leave your original dressing in place for as long as your surgeon says, and you will want to change it sooner if it becomes wet or soaked with blood or other fluids. Your surgeon will tell you how often to change it.
Changing it. Clean your hands before touching the dressing: wash with soap and warm water, clean under your nails, rinse, and dry with a clean towel. Have your supplies ready and a clean work surface. Put on clean medical gloves if the wound is infected, meaning red or oozing, or if you are changing the dressing for someone else. The gloves do not need to be sterile. Loosen the tape carefully. If the dressing sticks, moisten it gently with water and try again, unless your surgeon instructed you to pull it off dry. Put the old dressing in a plastic bag, take off the gloves into the same bag, and wash your hands again.
Putting the new one on. Make sure your hands are clean. Do not touch the inside of the dressing. Place it over the wound and tape down all four sides. Seal the bag of used material and throw it away.
Two things not to do. Do not apply antibiotic cream or other products unless your surgeon tells you to. And if you have non-dissolvable stitches or staples, your surgeon will remove them. Do not pull at your stitches or try to remove them on your own.
Clothing matters more than people expect: do not wear tight clothing that rubs against the incision while it is healing.
At some point you will not need a dressing anymore. Your surgeon will tell you when you can leave the wound uncovered.