Help me customise Endless

Hello all,

So I’m using the Endless theme, but need some help customising it.

If you look at a post: https://www.vgcuts.com/streets-of-rage-2/ you see the circle in the top right on standard posts with the date – I don’t want that there because the blog isn’t date-centered really. What would be so much better is if I could have a custom field for posts where I enter the year the game was produced, and that is what shows up in that circle.

Er, might be a tall order but I thought worth asking on here ??