There are a few ways to position a module through the PrestaShop back office. This also depends on the expected navigation of your web page. As mentioned, modules are, by default, positioned in particular sections of the page (or hook).
Here you will see a list of hooks (blocks) that you have installed and the modules within them.
Let's take an example of the right column block. You can see a list of modules, which are within the hook in the following screenshot:
Here you have the Cart block, the New products block, and the Top seller ...