In B4A, open the app. The current version appears under "Project Attributes" as "#VersionCode" and, if it is still the same as your original version, it probably shows "1". For the update, simply change this to the next higher integer (if it is "1", change it to "2") then upload the updated version. Users with your app installed will then get the updates automatically. For updated versions, you may also want to change the "#VersionName" for each update to something meaningful to you just to keep track of what you updated.