Left menu setup - Topic/sub toipc

I have just startede using Obsidian and I like it very mush.
But I have one things I cant figure out :slight_smile:

How do I get a menu in the left side with Topic and Sub Topics?
Like the one in the picture


Those are actually folders (on the first level with arrows beside then) or notes in the root folder (on the first level without arrows) and individual notes inside a folder (on the second level). You can add those by the corresponding icons on top of the left pane.