How to install a plugin/widget

Hi,

I am a complete novice on wordpress and am of a somewhat older generation so bear with me…
I would like to install a registration tool on my blog sidebar for visitors to register and start posting comments / articles or whatever.

I have absolutely no clue how to start. For the record I found a registration plugin with this “simple” installation directions:
1.Simply upload the registration-widget/ folder to your plugin folder, like any other plugin (SAY WHAT ?? I CAN’T EVEN FIND MY PLUGIN FOLDER)
2.Enter your WordPress Dashboard, go to Plugins, and activate Registration Widget as usual (AS USUAL ?)
3.Now in Presentation->Widgets there is a new one named “Registration form” that you can place in any sidebar. Use it as any other widget

HELP !
PS: Thanks for any directions !