How do I set up a Free Agent Acquisition Budget (FAAB) ?
Go to the Commissioner → Manage League → Transactions → Free Agent Transactions edit page. Select Yes to the Do you want your league to use a waiver wire to award free agent players? questions. Select the Blind Bidding Against a Waiver Wire Cap option and set the waiver cap (FAAB budget), minimum bid, maximum bid parameters.
See the FAQ entry http://faq.rtsports.com/doku.php?id=waiver-wire-setup for more information on setting up your league waiver wire.