You can modify existing draft templates by clicking Templates on the left side of the Editor. A list of existing templates displays in the Library.
Library

You can search for an existing template by clicking the Search button in the upper-right corner of the Library and typing its name in the Search field that displays.
Click the vertical ellipses icon on the right side of the row of the template you want to modify.

Click the Preview icon to open the template in Preview mode, or click Edit to open the template in Edit mode.