If you want to add a GIF to your emails, simply follow these steps:
Copy the shared link of the GIF from Google Photos, or copy the GIF shared link if you are getting it from Giphy.com
When you get the share link from Google Photos, paste it on this website to get an embed link that you can finally use in Instantly.
Paste it under Google Photos, then copy the Direct Image link.
Click on More Rich -->Insert Image
Paste the Direct Image link you generated or GIF shared link from Giphy.com
Make sure you click on "Preview" to test that the GIF works. You can also send yourself a test email to make sure it loads in the email.
You can watch the full detailed video by clicking the link here.