When you choose a deposit bonus, your deposit and bonus funds are locked until you've met the playthrough requirements.
The more you play, the more you progress, and you'll begin to see the funds slowly drip into your account.
You can check your playthrough progress on a bonus at any time.
Go to the profile icon at the top of the page, then click 'My Rewards' found under 'Active Bonuses'.
Click the drop-down arrow to reveal the details of your bonus in play.