This is second most common question you ask me. Read about first one here:
4. Take the iron and heat the sole (I did it on max heat, but take care and don’t burn the sole) from the wrong side (don’t iron on side where is the painting!) In this way the paint must puff! You have to be patient and heat it for at least one minute before checking the result, as it needs time to puff.
5. Now the soles are ready and you can work on upper parts. 🙂
Have a great weekend!