Here you can paste the copy of the Javascript code from the ad sense, or the affiliate program is offering. Ad sense or affiliate program will give you links using a particular Script code for ads maybe an image ad or a block text ad from Google in a Javascript code. You can paste it either:

Ads On Post Body,

You can locate it on the left, right, center, or none. You can choose pixel margin. You can store up to 10 forms ads here.

We have put one add for airport parking to the right.

Allows you to put the ads on the right or left widget as you like.

After you have done all the necessary changes you the changes and you adds will show up on your website as per your set up.

Added one ad in the widget of Big Commerce