Upgrading kodi

Hi all and please bare in mind I am totally tech incompetent. I have a android MXQ box, Google TV and it’s an old version so I can’t load up any new builds. I’ve tried to upgrade my kodi but just can’t see how I do this. I’ve tried from Google play but it just says it’s already installed. I’ve looked at the instructions on here but I can’t figure it out at all. Can someone please help as to the easiest way for me to upgrade.
Many thanks