Hey, welcome back Mysticpuma!
Mission4Today (the more active 1946 forum these days) has a detailed patching guide here:
https://www.mission4today.com/index....p=show&kid=584
If you want to do mods make sure you research which patch they are based on. Most are still at version 4.12, while the official game is up to 4.14.1 now. As you may know, the great thing about 1946 is that you can save as many copies of your entire game directory as you want. So if you think you might need version 4.10 (needed for the Dark Blue World mod I think) just save a separate copy at 4.10 before continuing the patch process to 4.12, and so on.
And I suggest you have a good read of the forums before progressing beyond 4.13.4. You see, patch 4.14 was a bad patch, causing problems with online play which are yet to be fully resolved. I'm running 4.14.1 as a stock offline player and it is fine, but some online players are not so happy.
Enjoy!