You can always look up individual tutorials for things you wanna include in your map, since training maps are all too different to be made with a single tutorial. Study things like bot behavior/nav meshes, I/O and buttons to control bots and the map, and
any of the TF2 entities if you need ideas for how to accomplish your ideas.
Edit: Also you could decompile existing training maps to inspect the logic and see how they did things.