how can i install the WOTLK version of the game for the new realm?
Does it work with 3.3.5a like the other realms or where do i get the old version of the game?
Is it under "Download" "Wotlk old" ?
And can i just use my old CDs for the installation, cause its fresh WOTLK?
Old CDs probably wouldn't work because it would query Blizzard and likely install Legion if it works at all.
"Wrath of the Lich King (Old)" is the 3.3.5a client with original character models, "Wrath of the Lich King" includes Legion models and is slightly more unstable but looks pretty.
You will need a program capable of downloading Magnet links to download from this website; uTorrent and BitTorrent are common ones.