Your Angel Investor total directly correlates to your all time cash earned. To receive the bonus from your angel investors, you must redeem them by performing a reset to gain Angel Investors. This can be done within the "Investors" page on the "Menu"; you just need to hit the "Claim Angels" button.
The formula for earning Angel Investors is [150 * the square root of (your all time cash earned in quadrillions)] – AI spent. This means that when you earn an angel investor, it takes more money for you to earn your next one.