There are several keys, you must go to steemit wallet and then permissions. You will see your public keys displayed. To the right is a button which says show private key. Click Show Key, next to your Posting key. Then enter your steemit password to reveal the key. Copy your private key paste it under your username in dtube and you should be locked into the blockchain!
@richq11, this is the answer to your friend's problem. @macmaniac77 got it right!