There are three methods to resize your image:
1. When you insert your image in to the post, you can set the size of your image by entering in the size of the height and width of your image. If you leave the height and width boxes blank, it will show the original size of the image.
2. After you enter the image URL, the image will appear in the post. You may click the image and drag the border line to resize it. Please note that this method is only available to the Firefox and IE browser. If you're using the Chrome or Safari, you may try the other two methods.
3. You can click the last icon on the top of the edit section to change the content into html, then enter in the width and height of the image.