I Need Help On Plug In: WORDPRESS SEO

I created a mini site and I used the theme News .02, however I found out that there is no way I can add the meta tags (meta keywords, meta description and meta title) in the homepage. I found out a good instructions by putting the html codes in the homepage. Then after few weeks, I got a good advise to add the plug in WORDPRESS SEO so I did but I forgot to remove the html codes for (meta keywords, meta description and meta title) that I added previously, before I install this plug in.

Is it okey to do this without removing the previous codes that I added? Will the new plug in over write those html codes? Most importantly I want to know if there is a TUTORIAL ON HOW TO USE PLUG IN: WORDPRESS SEO?

I would appreciate your answers. Thanks!