Then, can you please clarify for me the wording, "well-regulated militia"? Who does the regulation? How do you quantify "well-regulated" versus "poorly-regulat

Then, can you please clarify for me the wording, "well-regulated militia"? Who does the regulation? How do you quantify "well-regulated" versus "poorly-regulated". Do you have to be part of a militia in order to obtain arms? Am I breaking the law by not being part of a militia while owning guns?