Question on ads and other stuff

Hey, brand new user to this theme (and wordpress in general – noob alert!), and I think I figured out the theme so far. However, there are two things bugging me.

Homepage – Slider

So the slider one, there is that ad when you scroll down (clearly a sample ad) – how to I edit/change that specific ad spot to my own code? I can’t find it anywhere. Sidebar I assume is just typical widget adding, so I’m not worried there. I also want to insert some ads above the comments but after the content – how do I do that (on individual posts)?

I also can’t figure out how to change the default showings for the url when shared or looking at in the browser. Example – if you past the home url on FB, it says Homepage – Slider and Homepage – Slider for the description instead of the settings I set it too. Is there something I am missing here?