Fusible interfacing is interfacing that has one side with a ton of little dots all over it. When heated, those dots adhere to the fabric you’ve placed them on.
It’s super simple to use. The main thing to look out for is bubbling. If this starts to happen, quickly tear the interfacing from the fabric and start over.
So, first you need to cut your interfacing to the same shape as the piece it’s going onto.
and place it with little dots facing the wrong side of the fabric