https://launch.soe.com/eq2/
Go to that page and click on the Full button. That'll download the client installer. Run the installer and select your game installation folder and it'll put the necessary Launchpad files in place. Inside the game installation folder delete the "cache", "assetcache", "fixedassets" and "logincache-us" folders, then launch the game as usual. It'll take a while to download the full game, it's something like 12 gigabytes of game data.