How to install a third party plug-in?

Hi everyone, I'm new to openwrt and I'm trying to figure out a way to install a plug-in into the current firmware on my Linksys wrt1900ac and wrt3200acm. This plug-in is called ShadowSocksR Plus+ and it is hosted at

I would like to add it to my routers without having to re-build the firmware but I don't know how to do it. I see the files listed on the developer link but I don't how to actually installed through Luci or even SSH.

If someone can guide in the right direction, it would be greatly appreciated.

Thanks for the support!