How to install external plugin in Wordpress hosted on OVH?

Hi,

I am sorry if my question seem to be very rookie. I am very much of a beginner.

I'd like to create my own page. I have installed Wordpress on my OVL cloud. Standard Wordpress plugins are available and I use them. But now I would like to use a PRO version of some plugin. But in that case, once I pay I will receive a link to PRO version plugin. I need to install it on my Wordpress. The question is how. So far the only way I know on how to install plugins is to get them from Wordpress plugins store. I have no clue how manual installation shall be performed. Anyone can help?