Hi, and welcome to Scrivener and the forum! 
What about the organisation are you struggling with, specifically?
There are a few ways to move items in the binder: drag and drop with the mouse, right-click and choose the Move > To and then the destination container, or with the Ctrl+Up/Down/Right/Left shortcuts. You can also put the directional Move commands on the toolbar as buttons if you prefer that to the keyboard. Choose Tools > Customize Toolbars… and select the “Main Toolbar” in the upper right. The blue and white arrow buttons will be listed on the left and you can place them anywhere you want on the toolbar layout.
That’s the basic rundown on how to position items in the binder. Anything that’s intended to develop into part of your finished manuscript should be placed within the “Draft” folder. If you started with a template, this might be renamed to “Manuscript” or something else; it has the special white icon of a stack of manuscript pages with hole punches down the side:
Beyond that, how you choose to structure the binder is entirely up to you, and you can easily change it at any point in developing your project. Don’t get bogged down in “getting it right” initially. A lot of it isn’t going to be functionally important until you get to the compile stage, where you’ll have options during compile for how to format text of folders, documents, and document groups. At that point you can even handle documents at different levels in the hierarchy differently, if you want. If you’re working on a book with a lot of sections and subsections that will want to be numbered accordingly, for instance, that might be important for you. But many projects don’t ever need to bother with it.
The point is that Scrivener offers a lot of flexibility in how you arrange your project and how you treat it all later when you’re compiling it into a neat little package to take to another program or send off to your editor. There’s not really a “right way” to organise, just the way that works for you. To start off, I’d suggest just arranging all twenty of your headings as individual documents in a flat list inside the Draft folder. Then if any of those are sub-points to a bigger heading, move them so they’re subdocuments of that heading (e.g. select the sub-point and drop it directly onto the main heading to make it a subdocument). Or if you have a few headings that you realise could be part of a larger group you haven’t created yet, select them all and choose Documents > Group to place them all in a new container folder, which you can name appropriately.
You can convert a folder into a file and vice versa via the right-click context menu (or Documents > Convert). Both can have their own text and can have subdocuments, so the main difference aside from the icon is that they can be formatted differently during compile and that folders will load in the editor in a group view mode and documents will always open in text view. In other words, when you first select a folder in the binder, it will probably open in the editor as a corkboard with index cards showing the synopses of its subdocuments. From the View menu, you can change this to showing the subdocuments in the outliner or showing the text of all the subdocuments (and the folder itself) in Scrivenings mode. You can also deselect all the group view options and instead just show the folder’s text, the same as you’d see a single document in the editor. Whatever mode you select will be used by all folders until you select a different mode.
I strongly recommend taking some time to go through the interactive tutorial project, found in the Help menu or in the Getting Started category of the new project window (File > New Project…). That covers a lot of Scrivener’s features and will let you work through at your own pace in an actual project and will be a lot easier to follow than trying to sit and read the reference manual cover to cover. (The manual does have a Quick Start section, however, that may be helpful.) Then if you want further details on anything particular, dive into the manual to check out that specific feature. And of course if you have questions, don’t be afraid to drop a line in the forums. We have nice users who like to help each other out. They don’t bite (usually).
