In the 'Contact' section, you can edit the information on a Contact that you have already created. Open up your contacts and select the one you are wanting to edit.
Open up the contact that you are wanting to edit by clicking 'View' and you will be brought to their record, similar to the image below:
On the record there will be an 'Edit' button. This will allow you to edit the information of the selected contact. This includes fields such as name, telephone number and email address. It will also let you select whether or not the contact is currently 'In Use.'
Click 'Update' to confirm changes.