it helps to have an easy to use FTP program like Filezilla
go to File–site manager click on New Site
You need the proper FTP info from your host but it may be something like https://ftp.yoursite.com then click the button beside normal and input your username and password that you use to get into your site.
If you want you can choose to have your password remembered. Only do this if your computer is yours and fairly secure.
now click on connect.
You should now see your computer files as well as your site files.
Find public html or whatever the start point is for your site, click to where your blog is and look for wp-content double clicking will take you between files
under wp-content you will find a file called plugins
find the plugin file on your computer click and hold it and drag it over to the plugins file. it should now upload and you can activate from your blog plugin admin section.
here is a youtube on it https://www.youtube.com/watch?v=tjAXmtkoe_s