First ensure you have the rights to edit documents. I you are you can edit a document using the EDIT tab in the content bar. You’ll be taken directly to edit page. Fill in the form provided and click the Save button to commit your changes. You’ll be returned to the view tab where you can see how the document will be shown to users.

If you don’t provide the correct input on the edit form, when you save the document you’ll be returned to the edit page, and your errors will be highlighted. At this point your changes haven’t been applied—you must correct the mistakes and click Save again before the changes will be committed.