For an online coven you can browse through the covens on this site by going through the "groups" tab.
For an online coven you could try looking on WitchVox, many covens can be found there and you can search by location. However it is important to note that most real-life covens have a minumum age, this could be 18, 21, 25 or older depending on location and local laws. The minimum age is due to legal issues and coven choice, so if you are young or new to the craft maybe a real-life coven isn't the best idea.
What you could try to find however is a group of like-minded people to learn and practice alongside, which is less formal than a coven.