Right-click on the folder and choose Sharing and permissions. In the Permissions for the folder window, if the person isn't already included in the list of people you're sharing with, select to add them. Enter the name or email address of the person you're giving permission to, and then select Add. 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.