I am not sure which certification you are referring to in your question. If you are talking about the cert from the Aquatic Exercise Association, you need to go to their website (aeawave.com). This group does cert courses online and has workshops, but as to where and when, you will need to go online to see.
Do you already teach water classes? Are you already a certified fitness instructor? Is this a requirement at the location you are wanting to teach at? If you want more guidance, please follow up with some information about your situation.