Through Connections
Go to Connections in the menu.
Select the Friends category, then click on Requests and choose Sent from the drop-down list.
Click the Requested button next to the person’s name to cancel the request.
From the User's Profile
Visit the profile of the person to whom you sent the friend request.
Click the Requested button on their profile to cancel the request.
The user will not be notified about the canceled request. However, if you send them a new friend request later, they will receive a notification.