Social Media Section in Customizer Help!

In the social media section of the customizer, under social media icons, there are windows where I am supposed to add url’s for sites such as facebook, twitter, google +, etc., so that the icons for those sites will appear on my page and allow visitors to share my page on their social media accounts.

My problem is I can’t find a straight answer for “What is the share url for facebook, twitter, etc?” Every place I type in the question, the answers I get talk about code that is to be placed in the html of my page.

So… should I even bother with this function, or should I just figure out how and which php file to add share code to?

Because from what I have been able to learn, it seems that using the URL way will not add an image to the share button the way using code will.

Sorry if I haven’t explained myself very well, and thank you all for your time, patience and knowledge.