How do I UNDO a pick?

Accidents happen, and that's what the UNDO button is for.

If at any point during your draft you need to UNDO a pick (or several picks in a row), you can access the "Undo previous pick" option from the Commish Tools (...) drop-down:

Important notes:

For Auction style drafts, the Commissioner will only have access to this tool during the "Nomination" process (it is not available while live bidding is taking place).