Sitelink ad extensions can help boost your CTR and make your ads stand out with additional relevant page links. However, some sitelinks perform better than others and there are some sitelinks that may need to be re-worded or eliminated completely based on performance.
First, you'll need to set up sitelink extensions in at least one of your campaigns and your extensions will need to have been approved to run. Your sitelinks may not show all the time, depending on performance and ad position. Also, each sitelink needs to direct customers to a unique landing page. If a sitelink stops showing, check if it was disapproved and make the necessary edits.