How to Use Custom Thumb for Homepage?

I’m using ‘JNews’ Theme in My WordPress Site. My Homepage is selected as ‘Your Latest Post’. When I share my site URL or Homepage URL on Facebook or Social Sites, it’s showing my latest post’s Feature image as Thumbnail. But I want to show a Custom thumbnail for my Homepage. I’ve used Yoast SEO & All in One SEO but didn’t work. I don’t Know code. So please suggest me any plugin such that I can do the job. Thank you.

The page I need help with: [log in to see the link]