Click on the letter for the index of words and terms beginning with that letter. Then click on the word or term for the definition you need. Some older browsers may not be able to click down to the letter. If yours does not do that, you will have to scroll down the page manually using a browser button or a key like the "Page Down" key.
To return to the opening Glossary screen, click on your browser's "Back" button or press whatever key or menu takes you back to your previous screen.