OK. Well, in the .htaccess file you just need to do something like this:
You do a line like that for every redirect. So the red bit is the path to the original article, and the blue bit is the path to the page you are redirecting to. The path is really the bit after your domain name (such as mysite.com/blog/article/this-is-the-post).
Redirect 301 /blog/article/this-is-the-post /blog/whatever-page-you-like
Once you've set up the redirect, you can test it by trying to go to the old page, and the browser should be redirected to the new page.
By the way, this assumes that your site is hosted on the Apache server, whch most are.