Creating a mindmap is very easy with MindMaps WebApp. You will learn to make mindmap your own simply by looking through
the app. Integrated help is also available. I shall explain the creation steps for those of faint of the heart types. You start out with the 'central idea' which is already present there. Double click an idea to edit its text.

Move the mouse over an idea and drag the red circle to create a new idea.

Using Navigator

Use navigator panel to get an overview of your map. You can navigate around by dragging the red rectangle or change the zoom by clicking on the magnifier buttons.

Using Inspector

Use inspector controls to change the appearance of your ideas. Try clicking the icon in the upper right corner to minimize this panel.
Using Toolbar

Those buttons do what they say. You can use them or work with keyboard shortcuts. Hover over the buttons for the key combinations.

As such, there are many functions in this app. Most of them are self explanatory. Online help is also available.