full length first post and round thumbnail excerpts for all others

I’m trying to show the first post in full length on the homepage, and then every post after with the round thumbnail excerpts. Anyone know how to do that? I’m not very proficient with coding so a plugin is infinitely easier, but I do have a child theme installed if I need to edit it for this to work.

website is http://www.vegetablerhapsody.com

thanks,
Anna