Well we can not choose a coven for you, so go to the "Groups" tab and read the covens. Remember, some of the covens will ask for applications to be sent to the priest, priestess, and sometimes both.
Some covens such as "Spell Casters" will automatically let you in, except Spell Casters will automatically place you on "Council" position. Which will let you delete comments on the Spell Casters' forums and place articles and spells onto the site.
But the main thing you should do is read all the covens, or you know learn more on what you like to know, and then read the covens, and choose/send an application, to the priest, priestess, or both and wait.
So here are some places that might help you understand magick more;
http://www.spellsofmagic.com/read_post.html?post=369824 (Meditation Tips!)
http://wicca.com/celtic/wicca/wicca.htm (What is Wicca, Witchcraft, and Paganism?)
http://www.spellsofmagic.com/read_post.html?post=71692 (Starrie's Starting Out)
http://www.spellsofmagic.com/read_post.html?post=483942 (AwakeTooLong's The Basics: Expanded)
I hope these help you understand a bit.