If you have Parent Ads enabled, you can start creating and designing ad sections.
Creating an Ad Section
To create an ad section, simply click the "New Section" button
and choose the "Ad" option
Enter a name for the section and the number of pages you want the section to have. Then click Finish.
Designing an Ad Section
Click on the ad section you want to edit from your project dashboard
Click the Parent Ads tab in the left panel. From here you can see ALL ads or filter them by size. You may also check/uncheck the checkbox if you want to hide/show ads that have already been used on other pages. If you don't see any ads, then you have not approved any ads yet. See article about ad management here.
To apply the ad to a page, simply drag and drop the ad from the left panel onto a page. Then you can move the ad anywhere on the page. The ad sizes were designed to fit within the margins of the page (for example, a quarter page ad fills in a quarter of the space within the margin).
If you would like to add some borders around your ads for better separation, you can do so by clicking Add More>Shape>Rectangle. Remove the colored fill of the rectangle by unchecking the "Show Fill" checkbox. Then position the rectangle around your ad.