Will this plugin (https://wordpress.org/plugins/copyfight/) help me with my search engine optimization? It does make my content unique, it cannot be copied, but will Google still be able to index my content?
This plugin is only to prevent your content from being copied. There is no effect of it in indexing your site in Google. Google always index your website.
I think there is no effect you will get by using this plugin for SEO,better use some of SEO wordpress plugins like Yoast or All in one SEO pack its best.
The plugin you have specified protects your content and doesn't have any effect on seo , if your looking for some seo plugins then yoast seo and all in one seo plugin will be helpful Also optimize your site with gtmetrix to have a good page speed , site which loads faster are loved by google
Copyfight is used to protect your website's textual content against theft. There is no relation between site indexing and content protection. Google will definitely index your site. Also, You can use Yoast for SEO. Yoast is a bit more advanced tool offering better features and is also relatively easier to use. By far, it is one the best SEO plugin for WordPress I've come across.
SEO is just a nice side effect of Copyfight. Please try it and understand the power of your content remaining unique.