You get the hepatitis A vaccine in the muscle of your upper arm. Start the vaccine series when you're at risk of infection and at least 1 month before traveling. You need two doses at least 6 months apart.
There are also combination vaccines for adults that protect against both hepatitis A and hepatitis B. But these have a different dosing schedule. Ask your doctor for details. You might prefer this option if, for example, you're traveling to countries with high rates of both diseases.