What does the short code do?
Does it build a landing page?
Where should I put it?
The short-code generates the submission form that in the landing page.
You should build a landing page and insert the short-code to the page.
On WordPress it is easy to build a landing page. You just have to put together a headline, an image of your product, and a few lines of text (and the short-code of course…)
like our demo landing page: