On an android box like a Droidbox, you will be able to download Kodi direct from Google play store. Also Droidboxes come loaded with DBMC (Droidbox media centre), a Kodi variant tuned for android. On Amazon devices, Kodi has to be "side loaded".
You will still have to do some work to put Addons on the device. Either individually or by using a "build" prepared by someone else. Sean on this forum has a build which comes well recommended. Check his posts for installation advice. You can also install Addons individually - the Seo Michael web site offers very good advice on this.