If there’s instruction Install via Package Management, it means it’s extras for revo.
So if you’re using revo, there are 2 ways to install package.
1. Via Revo Manager, Point to System->Package Management anc click Download Extras button in the top of packages grid.
2. Download the extra zip file and put in the folder /core/packages. After that, go to the packages grid and click add new packages-->search for local packages.
Next, refresh the packages grid, and right click in the package you want to install.
If you’re using evolution, be sure to download evo version of extra. Mostly we need to extract the zip manually and do copy paste to snippet in manager. Just follow what Readme.txt/instruction says within the zip file.