Reward yields are paid every 24 hours, based on the balance in your account that existed 24 hours ago.
If you have made a new deposit (or added to an existing balance), that amount will not count towards accruing yield until it has been in the account for at least 24 hours. That is because the yield calculation for that day will already have begun.
In other words, if you have made a deposit at day T, you will start earning yield rewards at day T+1, and you will be paid out at day T+2. Therefore, you will begin seeing your rewards accruing 2 days after your initial deposit.
Everything is automatically calculated and paid daily, and you can expect your yield reward payouts typically between 02:00 to 05:00 UTC every day.
*Minimum amount to earn yield rewards is $1