Pre-heat fabric where the patch is to be placed for 10-20 seconds 

Place heat seal side of patch to the garment & cover with a fine cloth to prevent staining or damage from the iron 

Press the iron straight down for 30-40 seconds with as much constant pressure as possible (DO NOT GO BACK & FORTH)  

Turn garment inside out and iron back side of patch for 20-25 seconds.  

Let it cool then if edges lift or turn up repeat step 4 until adhered securely.