Open docs folder on your local server or if you working on the live website then open the website using Filezilla or control panel, whatever you are using.
Then open wp-content/plugins folder and paste your plugin which you want to add.
And refresh your WordPress dashboard and check installed plugin, that plugin you have uploaded will show up to you and then activate that plugin.
I have done this so many times, it works.
Note – first unzip your plugin folder and then copy the plugin main folder.