For someone to be able to edit your information you must first share it with them by setting the Share With controls.
Then you should check the edit box in the Share With control:
In the above image the user "jackie" has the right to both view and edit the shared information.
Whenever you check, or uncheck the edit box, be sure to give a Save command.
Sharing and edit rights are set on a document-by-document or item-by-item basis, or they can be set for an entire folder.
