This guide will help you install plugins for CMS3, doing following steps:
You can choose to install an already uploaded package or upload a new package to install.
You should make sure you trust the developer of the package you are installing, a bad plugin may bring down the system. Signature verification result: Press the button to verify the package.
Press the button belov to install the package, make sure you have verified the package and trust the provider. A bad package may breake the system, if you have any reason to distrust package distrobuter don't install the package. If you do anyway, make sure to take a look at the installation result, perhaps save it, it might be usefull if you have to restore a broken system afterwards. Installation result:
Press the button to install the package.