Most probably you would want to change the banners you have in the demos that you imported to your website. There are 3 types of banners we use in our themes:

1. Image banner
2. Widget banners
3. Theme options banner

How to change/remove page banner

This one is quite easy, you simply need to edit the page you are looking at and find the element. An example of this would be the VideoTouch banner on the homepage. Click the button to edit the page and find the element within the drag and drop builder blocks:

How to change/remove banners from widgets

First of all we need to see what widget are we using specifically. To do that edit the page (if this is a page) and check what sidebar is being used in that specific location:

After you click edit you should find the sidebar settings and the sidebar that is selected there:

After we know the name, go back to the WordPress Dashboard, Appearance->Widgets and find the sidebar and the widgets used:

Edit or remove the widgets from there.

Theme options banners

This is probably the easiest to find. Simply go to your Theme options panel and find the advertising tab. There you will find the available/used codes: