Casino bonuses update automatically in real-time as they are used. You can check progress of where you are with an offer on the promotions hub, and individual game pages. The balances shown in the site headers and 'My Account' will also update. You will clearly be able to see how much you have wagered and how much is left to wager.
Once wagering is completed, any winnings in the bonus wallet will be transferred over to the main wallet. You can check the details of this via the Account Summary in 'My Account'.
Bonuses have to be used in the order that they were awarded, in case the same Game is eligible to both/all of them. You can only use your next bonus once the current bonus has been completely used or has expired.
If you place a bet that is more than your bonus amount available, money from your main wallet will be used to make up the stake. It will not take money from other separate bonuses you have been awarded.
For example, if you have a £10 bonus and place a £20 bet, £10 will be taken from your main balance to make up the £20 bet total.