Mainly what you have to do is:

  1. Convert the site to WP
  2. Once all is good with WP edit .htaccess
  3. Above all the wordpress stuff you have to add this type of thing: Redirect 301 /myoldurl.html
  4. You have to add that for each old file that you want to redirect to the new file
  5. There is info all over the net, including here: