To use the Artifact Exchange you can turn in certain artifacts for 100 credits. Turn in by dropping one of the accepted artifacts onto Shen who is in Town Center just up the stairs west of the player vendors.
Right now you can turn in Greater Tokuno, Paragon and Gauntlet Artifacts in. More will be added later.
You can purchase a random artifact for 1000 credits.
You can purchase a random Paragon artifact for 2000 credits.
You can purchase a random Gauntlet artifact for 3000 credits.
You can purchase a random Greater Tokuno artifact for 2000 credits.