How to iron on patches:

1.Prep. First make sure that the backing of the patch is clear of any debris such as hairs, fuzz, lint or dirt. Next, you need to know what kind of fabric you are ironing the patch onto.
2.Choose the right temperature. The ironing temperature on clothes made of different materials may vary. Usually we use a heat press machine to iron denim clothes at a temperature of 185℃ (365℉), iron Pressure: 2.8-3.2, and the time is about 15-20 Second.
3.Iron on. If you use a heat press machine, just adjust the temperature and pressure as in point 2, and then iron.
If you're using an iron, depending on the size of the patch, try using only the tip of the iron when adding the patch. Start in the middle of the patch as the anchor point and move out from there. Keep in mind that the adhesive backing on the iron-on patch needs to be completely melted to bond to the fabric.
4.Let it rest. Once you are sure that the adhesive has bonded, take the iron off of the patch, and let your fabric and patch rest and cool down a bit. After about 5 to 10 minutes, you can lift the fabric vertically and see if there are any spots where the patch hasnt fully fused. If necessary, repeat the process until the patch is fully bonded.