Your $18.00 bought you a domain name. Only a domain name.
It did not buy you hosting.
With your domain name, your url link to your site has a name like this:
But you are still using wordpress.com with free hosting. The name does not buy you a different host. You must pay someone to host your site (to make it get online) or use a free host like wordpress.COM or Blogger or Tumblr.
You are hosted now on WordPress.com. You are still subject to the rules, regulations, and Terms of Service that you were before when your blog had the name like this:
Because you are hosted at wordpress.COM you will continue to edit your site http://seobasicwithmee.wordpress.com/wp-admin/
You cannot use plugins. WordPress.com users cannot use plugins.
If you need plugins you need to pay someone to host your site.
Please read this. You don't seem to know that there are different kinds of WordPress: wp.COM and wp.ORG. If you need plugins, then you must go to wp.ORG.