Modding tutorial

[Jelleh]

Hi all,

I want to make a simple mod for uboat.
I made my first project with this tutorial https://uboat.fandom.com/wiki/Moddin...ject:_In_Depth
The first thing i want to do, is to just add a button in the periscope views, just under the zoom buttons.
But i can not find any info how to just add a button in the game.
Is there some kind of tutorial to get me started with adding a button?

Thanks!