No tools needed and no sewing.
I purchased my grommets at JoAnns. They come in different colors--gold, silver, champagne, black, and tortise shell. There are larger grommets which I have used for curtains and smaller ones which I have not tried yet. These are the medium size. Directions are on the back. I'm a visual learner but let me tell you the directions on the package are very clear.
The package comes with a template. Lay your template top aligned with the pencil mark.
Trace your circle in the template grooves. Mark your bag front and back. If you're using grommets for curtains you make your panels first and then measure, mark, and install your grommets last.