Go to the time machine icon on the menu bar, click enter time machine. After your desktop goes into the stars animation, you should be able to see a list of dates of your backups on the right. Go to the backup date that you want to delete; In the middle, click the gear icon and click Delete Backup. Type your password when prompted More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.