Firstly, Yoast has written a really comprehensive guide on how to get yourself properly setup. Secondly, it’s not the kind of thing you need to get totally correct before you do anything else – you can tweak as you go. I would earmark half a day of your time to add the plugin and go through the above article making changes and then just leave it for a while.
The latest research from Google underscores the importance of having a mobile-friendly website. As consumers continue to spend more time on mobile devices, mobile page load speeds are critical to a good user experience. Over 50% of mobile users abandoning sites that take longer than three seconds to load, but most web pages take a lot longer to load, creating a significant gap between consumers' expectations and most businesses' mobile capabilities.