Some people were having trouble inserting images into posts (some of this trouble was my fault), so here’s a quick run down:
1) Make a new post
2) Above the formating tools, choose the “Upload/Insert” menu.
3) After you’ve chosen an image and uploaded it, click the “insert into post” button.
If you want to edit the placement or css of an image, click on the image, and then click the icon in the upper left. You can also look at the raw html in the html tag of the editor, but be warned that css doesn’t always behave as expected, since WordPress has its own css which might overwrite yours.
Hopefully this will answer any questions.