I just finished the lab quest in blood and wine and got the center circle on my character screen; how do i research mutagens to get the points to use?

It is not a matter of research - just skill points. You will need 2 skill points and some greater mutagens for the lesser ones in the tree. The skill point cost increases as you reach further into the tree. Note that you can only have one active mutagen at all times, so you may want to plan a starting "pathway". In the end you will want all of them for the extra skills tabs, but this can only be fully accomplished in New Game + (simply because it takes so many skill points).