You can edit an organization/contacts information by clicking on the green edit button 
in the Actions column for that contact. This will bring you to the Edit Contact/Organization form. Here you can modify any contact information. This will have the same fields as the Add Contact/Organization form. Go to the Adding Contact section of the manual to learn more about the form.
*If you do not see the green Edit button, it is because the screen is too small and you will need to expand that entry by first clicking on the green plus icon 
immediately to the left of the entry.