https://dcuniverseonline.fandom.com/wiki/Test_Server. should be right here, just click the site link and then the download link on the wiki.
While the above link will at least help you download the client, please note that the DCUO Test Server is currently down and will be so for the next few days. https://forums.daybreakgames.com/dc...owntime-february-14-2019.300848/#post-4212839
Oh i know i wish it was Justice league dark but for some reason i think there having problems with it cause they don't know when its going to be up
The test server is down because nothing needs to be tested at the moment, the devs are focused on fixing the issues on Live.