Without an image source file, the Text box does not know where to pull the image from. Because of this you would not be able to copy paste from a word document because there isn't a image source file to locate on the web.

You can load a photo to the text box directly from your computer and set the size limitation for photos in text content.

To set the size limit go to 
  1. onCampus
  2. Settings
  3. Academics
  4. Course Content Category Settings
  5. Edit Text
  6. you can then set the max width and height (this will only affect new photos that are added and any existing photos will need to be removed and added again to follow this change.

Users can then go to the group page bulletin board and click on 
  1. Edit Bulletin Board
  2. click the edit pencil icon next to the text box
  3. select a photo from computer
  4. Save