To add GIFs to your email prospecting template simply go to Email Templates section and click the template which you wish to edit, or create a new template.

Check that your GIF is in the correct format (.gif), then click the Insert/Edit image icon and add the GIF straight from your computer. If you are unable to add them through your computer, you also can paste the link of the GIF and click Save.

Should you need to adjust the size of the GIF to fit your email template, you can do so by adjusting the width and height as shown below.