Installing SSL Certificate on Wordpress site

I have paid for a SSL certificate for my WP site and need to a) run a back up. I use the PlugIn BackWPup, but when I try to run a back up, it only gets half way through and then shows me the Warning attached below. b) activate the SSL certificate using the Really Simple SSL plug in which requires the following: i) Http references in your .css and .js files: change any http:// into //
ii) Images, stylesheets or scripts from a domain without an SSL certificate: remove them or move to your own server.

Many thanks.