render-blocking JavaScript and CSS

When I run Google speed check, I get this
Eliminate render-blocking JavaScript and CSS in above-the-fold content Your page has 3 blocking script resources and 7 blocking CSS resources. This causes a delay in rendering your page.Approximately 66% of the above-the-fold content on your page could be rendered without waiting for the following resources to load. Try to defer or asynchronously load blocking resources, or inline the critical portions of those resources directly in the HTML.Remove render-blocking JavaScript:https://davidsgifts.co.uk/…-includes/js/jquery/jquery.js?ver=1.12.3https://davidsgifts.co.uk/…s/jquery/jquery-migrate.min.js?ver=1.4.0https://davidsgifts.co.uk/…ns/wp-quick-organizational-tree/js/js.js

Can anyone explain in step by step plain English way how I go about fixing. I do have a plug in installed, which did get rid of some of it, but not these three.
Thanks
David