Once installed, the extension will be available every time you open an email in Outlook, but the method of opening it is slightly different depending on whether you are using the traditional or new layout of Outlook.
Standard Layout Outlook
Click the icon shown when you open an email.
New Layout Outlook
Click the icon shown when you open an email. This will open a panel that contains the Ezekia dolphin icon.
Pinning the extension open
In either version, once the extension is open, you can 'pin' it using the icon shown below. It will now stay open every time you change emails, automatically refreshing to show the details for the latest email.