The Scroll/Link sticker is used to link consecutive slides together yielding a single, scrollable page within your app.
To illustrate the effect of the scoll/link sticker, consider the following scenario, the first screenshot showcases two slides, each with the link sticker, hence stitching them together, effectivly creating a single page.
Note the two link stickers used
The final app, note that both slides are rendered as a single page
If you remove either link sticker, each page will be treated as separate pages.
You can have only one link sticker per slide.
When you should use it
Use the scroll/link sticker whenver you want to group content into a single page. The sticker must be placed on all slides to be linked and all slides must be placed consecutively.
If you need to begin a new page following a series of linked pages the link must be broken using another page or a section header slide.
There is no special configuration for the link sticker. Simply stick it on your slides and it'll work its magic when you publish your app.