Assuming your links are text and not buttons, do the following:
1. Click on the lettering of the link so that the cursor is somewhere within the link text
2. Click on the Hyperlink icon on the top toolbar (looks like a miniature planet Earth with a chain link at the bottom) or right click on the hyperlink text on the page and select Hyperlink Properties from the drop down menu.
3. In the Edit Hyperlink box that pops up, you can enter anything you like where it says 'Text to display:'
4. Click OK
5. Save the file, repeat on all pages as necessary and then publish the site.
If you used buttons the process is roughly similar but you need to double click the button to open it for editing.