To access files that have been shared with you, simply click on the share link that has been provided to you. If the share you sent is protected, you will be required to enter a password (which should be provided to you by the sharer of the files) before accessing the content.
You will then be directed to a Shared Files page where you can access, forward, or tweet the content that has been shared with you.
For information on how to share files, please click here.