The 'Rich Text' module provides a rich text area that can contain formatted text, images and display links to websites and uploaded files.
To edit a Rich Text module, click the edit tab on the top of the module. A toolbar will appear with icons that will probably look familiar to you from other text editing software. If you don't recognize any of the icons guide your pointer to them and hover - text will appear to tell you what they are.
Use the rich text editor to enter and format text, add files, add images and web address links. You can build tables, spellcheck and make a find and replace search, among other features. You must hit 'Save' before using any other function or module, and also before 'Publishing' your work.
You can always go back and 'Edit' this information, and then 'Save' and 'Publish'.
For more on the Rich Text Editor toolbar, see this article: