"Unlike our traditional Test client, your match history, MMR, cosmetic items, and friends are shared across the two versions," Valve's announcement reads.
"However, Ranked Matchmaking is not enabled yet. We anticipate that we'll be able to turn it on in a few days, but we need more testing of the basic functionality first. Also, it is possible new items may make their first appearance in either the beta or the main client. These items may be temporarily missing from the other client while their assets are converted."
Check out the update page for information on how to access the beta.