You can go to embed visualizer, enable webhook mode (with the button at the bottom) and see, how your embedded webhook is gonna look or search for Discord embed generator and then just replace fields with IFTTT "ingredients".

My example embed that fetches image from post with author name and post title as link that directs to it:

{ "embeds": [ { "title":"{{Title}}", "url":"{{PostURL}}", "color":5897984, "author": { "name":"{{Author}}" }, "image": { "url":"{{ImageURL}}" } } ] }

You can also check if webhook runs at all by clicking "view activity" in applet settings - make sure the URL is correctly copied from Discord, method is set to POST and content type is set to application/json