RE: how do I edit a MySQL database?
If you have command line access, you can interact with your databases through that if you know SQL. If you are accessing it remotely, you'd have to ssh or telnet in.
If you are interacting with your db's through your website, you could interact with your database by writing code in your website to do things (read/write/edit) using technologies like PHP. This also requires knowledge of SQL.
If you have MySQL management tools as bill and theodora have mentioned, you can skip knowing SQL and use the tool's GUI to do stuff. I use phpMyAdmin, a web-based tool that your web host may already have installed for you.
I'm afraid I do not know much SQL, but what I have learned I got from the MySQL manual. I keep my MySQL and PHP manuals open and available everytime I work on web projects using those technologies. There are also lots of tutorials out there to learn the basics.
Hope this helps some!
--ST