Just to clarify, are you wanting to transfer your domain from WordPress.com so that you can self-host it using with full control of your site (i.e. full control of themes, extending functionality via plugins)? And, is the domain that you are referring to the one that is hosted here at WordPress.com called: teachingresourcesfortheclassroom.com?
If that is the case, you would first need to purchase a web hosting account, setup the WordPress.org site and then transfer all of your content from your WordPress.com site to your new hosting account. If you are using the same domain name, instead of site redirection, the domain name servers would just need to be updated to point to the right host - Update Name Servers or Change Name Servers.
If you would like to have the extended functionality with plugins and full control over your site, it does make sense to switch. WordPress.com also offers a service called a Guided Transfer if you are unable to do all the initial work involved necessary to switch over.
I hope that the above information is helpful. Best of luck to you!