Interest begins accruing the day after you fund your account, and is paid out on a monthly basis at the end of the month. Interest compounds monthly, so after you receive your first interest payment, the next month interest will accrue on your original principal + interest earned!
For example, if you fund your account on the 15th you will earn ~14 days worth of interest. If you fund on the 20th, you will earn ~9 days worth of interest. Each instance is prorated based on the number of days that the balance was in the account.
Interest Account Statements are available on the first business day of each month.