After your beats begin to be monetised, payments will be made at the end of each month. (The exact date will depend on when we receive the payment from YouTube)
Payments are made a month after they are earned, so you'd receive January's revenue at the end of February, February's at the end of March, etc.
It could take up to 3 months for you to receive your very first payment* as it also takes 1-2 months for your beats to actually become monetised. After this, payments will be made to you monthly*
*Payouts are only made once your earned revenue is above $5. If you have not yet earned £5, it will be paid once you have earned above this amount.