Hi,
at the way to download and instal the game nothing changed at the last years it is still the same procedure.
You got an email from Sendowl with the notification of a new version, but basicly any email from Sendowl works, the link inside that email is allways the same personal link for you.
- Open the link and download the version for your OS.
- Delete the old installation folder.
- Unzip/copy the dowloaded file at the folder you like.
- Find the execuble file (for windows RimWorldWin64.exe) and start it.
Since you download directly you don't have steam Workshop support and when you like to use mod's later, you should check the 1. link of my signature.