Just below the text editor, you have the option of uploading a variety of files such as .jpg and .gif files. Browse and select the file you want to upload and you have the opportunity to add in a title and/or description. Then click upload.

The next box to open will allow you to choose how your image will appear; thumbnail (tiny depiction), full size, or title (the title of your image which you can then decide to link to the full size image). You can also choose to link your image to another file, page, or nothing. Once you have made your decisions, click Send to Editor.

The image will then show up in your text editor.