Hello!
There are several resources available to you. I would start by reading the wiki entry here:
And of course Epic’s official documentation here:
Of course, the best tutorial you could ever have is in the source code itself. Browse to Engine/UE4/Plugins/ for Epic’s own in-engine plugins.
I would recommend the Plugins/Developer/BlankPlugin/ in particular as it’s their own “sample barebone plugin”
I wish you luck 
/Temaran