I haven't updated since I bought game....still using Alpha12. To update, I need to completely delete Alpha12 or just the data file? Will be able to use saved games from 12 on 15?
as you were using a12 (assuming you did download it from sendowl), just download the latest version from the SAME link that you got the a12 from, (it will be a zip file), then extract the zip to the same folder that contains the a12 folder, this will create a new a15c folder, inside the new a15c folder you will see a rimworld1284xxx program, run the rimworld program