I thin the bulk of the fleece or interfacing around the grommet making sure I still have some on the inside of it. Then I place the parts, and once get them lined up use a small hammer to put them in place, so far no problems. I have had to call my DH in for extra strenght in snapping them in if they give me fits. So far have not used glue on mine or read that in any of my instructions.
A friend told me she saw a tute on you tube about this but haven't looked for it so far.