kodi 17 on android box

Hi
new to android box and new to forums so hope i do this right,I bought a second hand android box with kodi 16.1 on it,I want to install kodi 17 but it wont do it.no option to delete kodi only restore factory settings,I saw somewhere on it it was running lollipop 5.1 or something like that.I went to official kodi site and download all the arm downloads,tried them all but just says app not installed,has anyone any idea what i,m doing wrong