To opt into paying just 2% commission, simply visit the 'My Account' section of your Betfair account and select the 'Basic' rewards plan. The 2% commission rate will be applied to your account immediately and you can start making those commission savings.
To use your free bets, add your Sportsbook selections to your betslip that meet the terms and conditions of the offer. You'll then be able to select to use the free bets through using the 'Use available bonus' toggle at the bottom of the betslip.