Once a day you will receive a Daily Bonus in the form of credits at Slotpark. As soon as the Daily Bonus is available, a window will open when starting Slotpark. 

The bonus amount depends on your current level and the number of days that you have played Slotpark consecutively. If you play daily you will get a higher bonus.

You can set a reminder to avoid missing a Daily Bonus. Alternatively you can enable reminders in Settings.