Hi,
There’s no userguide, but there are some faqs here:
https://www.ads-software.com/plugins/fast-velocity-minify/#faq
Beware that this plugin is meant to be used by someone with at least, basic developer skills or at least, power users that understand what some of the terminology means (defer js, async, minify, etc).
You can obviously try to install, since if your site is simple enough, it should work fine. If it’s not, you can try to read the faqs, and if that also fails, let me know.
You may also want to hire a developer to help you with the speed optimization on upwork.com or freelancer.com