I just received an email offering me 5.20% interest on a 12-month certificate of deposit. What a time to be alive. I have a high-risk appetite, so CDs don't do much for me; however, they can be essential to your portfolio. CDs can serve as your first step into a much larger world of investing. You can use the interest payments to invest in higher-yielding securities and strategies-I call it "High-Yield CD Reinvestment." There...