Cumulative preferred stocks pay dividends. The dividends come from the company's profits. Typically dividends are paid quarterly, but this is not always the case.
Preferred stock payments are generally expressed as an annual interest rate so 8.5% cumulative preferred would most likely pay 2.125% of face value quarterly. Face value is usually $25 for most preferred stocks but this can vary as well. If face value is $25 and the preferred stock pays 8.5% annually, you could expect to receive $0.53125 per share owned about every 3 months. So if you owned 7000 shares of preferred stock you would have $3,718.75 deposited into your brokerage account on the payable date which would be announced by the company's board of directors.
Remember that preferred stocks are junior to all of a company's other debts. Even cumulative preferred stock dividends can be suspended if a company is facing financial hardship. If the company survives the difficult time, these dividends must be fully repaid before any common stock dividends are paid, however there are no guarantees. In the event of bankruptcy, preferred stockholders usually recover little if any of their original principal.
Be sure to invest in shares and a company that you fully understand. If you do not understand, consider talking to a professional investment advisor or stock broker.