How can I change my battery?

Whenever I restart the computer, it tells me that I need to replace the battery, which hardly lasts 5 minutes if I unplug the power adapter unfortunately. I searched HP's store site and couldn't find any batteries that were compatible with the Pavilion 11x360, but I managed to find a compatible battery on Amazon. I am not sure, though, how I would go about replacing the battery if/when I were to purchase the new one... There is no slot underneath the computer where the battery is visible, as there have been on all of my previous laptops.