Hey man! I know how you feel, everyone of us was at your place, but.. no worries.
It's not that easy to play this game, you need to have advanced computer skills.
1. You need to download and install Java
https://www.java.com/en/download/2. Your autohaven.jar file should have icon like on the image

3. Double click autohaven.jar and it should work.
Apologies for inconvenience. Our Developers didn't bother to create separate downloadable packages per operating system with build in Java.
The game doesn't have proper tutorial. I am sure our developers forgot 90% of the game mechanics. Take a look on player made wikipedia:
https://ringofbrodgar.com/wiki/Haven_and_Hearth_Wiki. Be carefully, information there might be inaccurate!
If you are casual Stardew Valley player you can stop reading there.
------------------ IMPORTANT ------------------ After you play a bit you will see that default client is not useable. You have a few options
1. Improve default client by yourself with new features. There is repository:
https://github.com/dolda2000/hafen-client. You need to have Java skills and patience.
2. Check out our wizard towers forum:
viewforum.php?f=49 and download one of publicly available clients.
But.. wait a second
There are 2 version of the game, one with old resources and one with new resources. Support for the old resources will be dropped at some point.
Currently the best client with old resources is:
https://github.com/Cediner/ArdClientCurrently the best client with new resources is PROBABLY:
viewtopic.php?f=49&t=40754.
Then.. another question:
Are you into PvP or PvE?
If you are into PvP you have to hire full time Java developer to adjust default client with must have features. If you don't have PvP features, play only PvE and run away from anybody you can see.
Enjoy!