How do I install a plugin (newbie)

Hi I am a complete newbie and I apologise if this question has been asked many times , I did search for some time but struggled to get an answer to my question , im sure I will get better at searching.

What I am trying to do is up load a plugin so that I can play a video directly in my blog website by just pressing the play button on the web (its a very short video) I think I could manage the hyper links back to you tube and stuff but I want to have this particular video play directly from my site . research suggests I need a plug in to do this . I down loaded the vipers video tag but then struggled to get it installed in wordprees dashboard
I’m sure you realise I’m a numpty but help with this would be much appreciated

cheers