After installing the module, i go to the product page and i only see the tab. I don't see the other produts that people usually buy.Do I have to wait until customer buy again so the module start recording those records? 

Doesn't work with all pre exsiting orders? 

thanks 

AlsoBought creates its own records for usually-bought-together product pairs. Uninstalling the module clears all the already generated records. That is why you cannot see any usually-bought-together product pairs immediately after the module installation. You should wait until the module generates again records for the usually-bought-together product pairs.