If your WordPress has the option “Your homepage displays” set to “A static page” (under Settings » Reading), then creating a Heatmap test for this page is very easy: just select that page in the page selector when creating the test:

If, on the other hand, your WordPress has the option “Your homepage displays” set to “Your latest posts”, then when creating a Heatmap test check the option Track heatmap of a page specified using its URL. This will display a field where you can type the URL of your homepage directly:
