Upload the image using the Desktop Media Uploader. You can install/run it from the first screen that shows when you click the "Media" section.
Click where you want the image. Select the tree icon.
Browse to the folder and select the image. You can resize it using the width/height pixel sizes.
If you need to wrap the text around the image, click on the image and go to styles, selecting "embedded picture."
You can right align using the alignment tools.
If you need more control over the margin, click the HTML button and look for an <img src="URL" />. Add style="margin-left:10px;" after the src="URL" and before the />. Change the margin-left to margin-right, etc.