If the link is in an email that has already been sent then you will have to first make a copy of the email in order to get into it and edit it. If it's a Draft email, just go to the block that has the link in it you want to change. Then follow these steps:
1. Place your cursor over the link and click Insert Link.
Use the editing options to:
-Change link text color - Click the drop-down menu to select a color. Click More Colors to refine your choice or add a specific hex value.
-Add or remove emphasis - Click Bold, Italic, or Underline.
-Edit the link text - There's no limit to the number of characters for your link, but keeping it between a few words to a short sentence looks best in your email.
-Update the URL - Enter a new URL or select a previously used URL from the drop-down menu. Don't forget to test the link to make sure it's working correctly.
2. Click Insert to continue editing the content in the block.
3. Click Save to continue editing the rest of your email.
4. Once you've finished making edits, send yourself a test email to see what your contacts will see.