Content is edited by first displaying the Content.  You can use the Menu system to find the display for the Content.

Or you can use the Content in the Administrator menu bar and find the Content you want to edit.

Once the Content is displayed, the Edit Tab will be are the top of the Content. Click on that tab and the Content will be displayed in the form that created it.

Editing can now be performed.

Be sure to click on the Save button on the bottom of the form.