Go to Account → My accounts → Demo.
Select the demo account you want to adjust, then tap ‘Adjust balance’.
Enter your desired balance amount and tap ‘Confirm’.
Your demo account starts with a default balance of 1,000.
You can top up your balance in increments of 10,000.
To do this, go to ‘Settings’ → ‘My accounts’ → ‘Demo accounts’, then click the ‘Top up 10,000’.