Logging on through Blizzard

[Shenesio]

I currently have fully up to date WOW, do I still need to download the Nostalrius client to play on the realm? Can't seem to do it by just changing the realm name.

[Same]

You will need a 1.12 client with the correct realmlist in order to log into this server.

Same.

[Taibak]

Go download this installer (you can have it installed in a separate directory and keep retail WoW).

https://mega.co.nz/#!4wlghKjR!1zYwN0VC8 ... i8P56muwcE

Download this replacement realm.wtf file into that install directory and you're good to go: https://en.nostalrius.org/assets/realmlist.wtf

[Aunstic]

I currently have fully up to date WOW, do I still need to download the Nostalrius client to play on the realm? Can't seem to do it by just changing the realm name.

I don't know what you mean by "fully up to date WOW", but updating the patch after installing the client will install the latest retail patch.

Download the realmlist.wtf In the post above mine by Taibak and replace the realmlist.wtf inside your WoW folder with Taibak's file.

If you receive an "Unable to connect", "Disconnected from server", or any other error while logging in, this may help as well. The client may have picked one of the test realms which might be your problem here.