How to add a 'checkbox' input that will appear on each blog in a layout

I'm using the Astra theme on Wordpress and the grid layout for blogs. I would like to add a 'checkbox' input button in the php so that each blog post not only has it's own 'read more' button for instance, but a checkbox as well. The checkbox will serve another purpose but I won't get into that. In this case, if you are not familiar with Astra, each blog that appears in the grid layout is an 'article' as you can see if you go to https://webux.dev/post-grid-hover-fx/ . So, I would like the checkbox to be inserted within the 'article'...but I suck at php and don't know how add this thing in the the child theme functions. Any of you know how?