Choose image displayed on Facebook when adding a post

On version 3 of Easyblog I used to be able to choose a picture that would come up with the post on Facebook.... (to be honest I didn't really understand how it worked BUT on Facebook either the default picture post I had uploaded called "default_facebook.png" would be posted as standard or sometimes it would choose a picture either from the main page of the blog or the blog pic on the right hand side - at least some picture came up!!)

Now it seems that Easyblog 5 is far more focused on options for each individual blogger (which is fine except for me it ends up being a bit more work as the BLOG is more important to me than whoever posts to it - this is just my situation and maybe it's different for other people...).
So the blogger picture comes up as default (and in my case I don't seem to be able to change it in any of my websites for some reason so it's just a generic avatar icon) but I would like to have the choice of which picture comes up in facebook when I either autopost to facebook or simply copy my blog article url to facebook... How can I achieve this? (and it that something to do with OpenGraph?)

Many thanks, Kyle.

P.s overall I think there could be more hover over tips for what does what in the blog composer window... eg if I add a picture in the blog does that become the default pic when autoposting to social media sites? If I add a cover photo where does that actually appear? what's the difference in the blog between APPLY and Publish Post when either creating or editing a blog post? maybe even a preflight summary before a post is posted would be handy so we know off hand whether we've added SEO, whether there's the default picture setup, which social platform will be posted too etc... just an idea...