Adding a linked image into a sidebar widget:
Step 1: Upload an image using the media uploader (Media > Add New) Make sure that the image is no more than 200 pixels wide BEFORE you upload it.
Step 2: Copy the file URL of the image you have just uploaded.
Step 3: Go to Appearance > Widgets and drag a text widget into the sidebar
Step 4: In the box type the following html:
<p align=”center”><a href=”ADD YOUR LINK HERE“><img src=”ADD THE LINK TO THE IMAGE FILE HERE“></a></p>
Replace the bits in capitals with a link to your school website (or wherever) and the link to the image file. Now save.
Once you’ve done this you’ll have a linked image in your sidebar, like this one: http://newzealand.blogtheworldcup.net/