To enroll in a health insurance plan under the Affordable Care Act (Obamacare), you can visit the official health insurance marketplace website, healthcare.gov. There, you can create an account, fill out an application, and browse different health insurance plans available in your area. You may also be eligible for financial assistance to help lower the cost of your health insurance premiums. Additionally, you can enroll in a plan during the annual open enrollment period or qualify for a special enrollment period if you experience certain life events, such as losing other health coverage, getting married, or having a baby. It's important to note that each state may have its own marketplace, so you should check if your state has a separate website for enrolling in health insurance under Obamacare. Seeking assistance from a licensed insurance agent or navigator can also help you understand your options and navigate the enrollment process effectively.