How to decide where module will appear?
Firstly it is necessary to say that module can have two views: one on the back office (its options, or even a configuration screen - as i described in previous steps), and one on the front office. The front office view is how and where the module is displayed within your shop's theme. The position of a module in your theme can be changed, because you might want one module's block to be placed much higher (or lower) in the page that others. In PrestaShop's parlance, this is called "transplanting", and is done using the tool available in the "Positions" page, So if you want to decide about where module will appear you can use this tool. Below you can find informations about this feature in context of Product tag icons module.