Hey,
Editing the admin panel to store the teams in an SQL database might be difficult for you as it is not like flipping a switch (changing a setting).
There are many resources already made for this in the community site.
Check here: https://community.multitheftauto.com/index.php?p=resources&s=list&name=teams&descr=&category=
Some of them are reading a teams.xml file which contains all the teams and their details like name, tags, colors (you will have to manually add them in this file).
And there are ones that get the current created teams (i.e. by Admin panel) and once the resource gets stopped (or server shuts down) it saves them in a file and once the resource is started it creates them back.
Just try them and use what fits your needs.
But if you want to create your own resource (and have scripting knowledge) we can help you if you are having hard time making it.