Its just too easy.
Whenever you uploading the model in Grab-cad library or workbench , there should a place in which the page asking for "URL to video"
Simply provide the URL to video and your animation will be live at Grab-cad model review section (Means in your model page).
You have to create an account in You-tube to upload the Models animated video.
In youtube just set an name for the channel you wanna create than upload the animation, after successful upload it will give the video URL to view the animation in You-tube.
Than copy that url and put in the Grab-cad URl requesting page (When you upload the model or just click settings in existed model in your library).