How to change an image?
Step 1. click Site Actions of the top right of the screen. Click Edit page.
If pop-up a security alert, Just click Yes. If you encounter it each time, just click yes. (I change the configuration for the site, so it maybe will not appear again. Please ignore this step.)
Step 2. click Edit. Click Modify Shared Web Part.
Step 3. Maybe you will get an error. (But sometimes there is no this error). That is because this Page has been modified since you opened it. You must open the page again.
Click Refresh page.
If you encountered step 3, you have to re-do Step 1 & 2 again.
Step 4. Click Rich Text Editor… on the right side.
Select the picture first. Then click cut icon. (Or you can delete it by using Delete button on your keyboard.)
Click Insert image icon to insert an image.
Select Browse button to select an image.
Click Current Site Images.
Select a picture. If you don’t upload the image to SharePoint before, click Upload button.
Then select a picture you uploaded. Click OK.
If you cannot see the picture you uploaded, click the next page.
Step 5. Click OK on the HTML Editor Dialog.
If you encountered the error of step 3, you have to click Publish on the top left of the screen. Then re-do all steps again.
Step 6. Click OK on the Content Editor Web Part on the right side.
Step 7. Click publish after change all the contents. This step is very important. To make sure other users can see the changes.