I bought these patches several weeks ago. I want to know how I can stick these patches. Do I have to iron or do I have to sew on cloth? Can I stick it to velcro also by using iron?

I would agree. I have had to deal with over 2000 patches in my time so far. I have never gotten my iron hot enough to keep patches on . Sew it and it's done.

Sewing is the best option. Some have a backing that has an adhesive that sticks it on with heat, but I've never been able to get my iron hot enough to make it work. You can buy velcro, but that would mean sewing it to the back of the patch and on the clothing item. Hope this helps.