It's self explanatory if you ask me. The forum's BB codes and tools are very much similar to that of your regular HTML 5 codes which simply means if you have a basic understanding how HTML formatting works then you should be able to use the forum syntaxes without any issues all you'll have to do is replace the angled brackets with square brackets.
I don't think there are guides specifically about these tools. Although I have created one about most tools generally I didn't make emphasis on basic usage of how each tool syntax works.
BBcode and HTML are very similar, but it depends on how a beginner is whether or not they are familiar with HTML.
Even if you don't understand HTML and BBcode, you will start to be able to do it if you are used to practicing in this forum.
I didn't know at all at first, but then I kept learning and trying each guide and understanding how BBcode works.
And some guidelines have also been explained, just learn them.