At times, for hyperlinks in particular, a special code must be added to the HTML to make the hyperlink bold.

Starting point: editing the content
  1. Navigate to View>HTML Code
  2. Search through the code for the URL you're wanting to bold
  3. Locate the section noted similar to: <a href="linktoboldhere"> text for the link</a>
  4. Add style="font-weight:bold" in between <a and href. 
  5. It would look as follows: <a style="font-weight:bold" href="linktoboldhere"> text for the link</a>
  6. When finished, click Update
  7. Then, Click Save