Slow Site

I am experiencing a very slow site.

Have carried out a test which identifies the follwing:

https://mywebsite.com/wp-includes/js/jquery/jquery.js?ver=1.10.2
https://mywebsite.com/wp-includes/js/jquery/jquery-migrate.min.js?ver=1.2.1
https://mywebsite.com/wp-content/themes/directorypress/PPT/ajax/actions.js?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/PPT/js/jquery.selectBox.min.js?ver=3.6.1
Optimize CSS Delivery of the following:
https://mywebsite.com/wp-content/themes/directorypress/PPT/css/css.premiumpress.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/PPT/css/css.homepage.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/template_directorypress/styles.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/PPT/js/jquery.selectBox.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/themes/directorypress-Clean-Directory/css/_purple.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/style.css?ver=3.6.1
https://mywebsite.com/wp-content/themes/directorypress/PPT/css/css.framework.css
https://mywebsite.com/wp-content/themes/directorypress/PPT/css/css.960.css
https://mywebsite.com/wp-content/themes/directorypress/PPT/css/css.ribbon.css

I have switched off all my plugins and the site is still extremely slow.

Tests on Google PageSpeed insights recommends that I

Eliminate render-blocking JavaScript in the above-the-fold content – and this appears to be the biggest cause of slowing.

Any suggestions on how to improve this?