What is it? Studying Abroad is when a student travels to a country other then the one they're from for educational opportunities. Students are able to learn more about the country they decide to go to such as language, culture and possibly religion.
How can I sign up? There are various ways one can sign up for studying abroad. One option would be to ask your counselor about the opportunities or another option would be to go to a reliable website such as http://aglifesciences.tamu.edu/international-programs/students/how-to-sign-up-for-a-study-abroad/ where they offer a variety of different programs for whatever suits you.
How will I pay for it? Studying abroad offers plenty of scholarship opportunities for students. Websites like the one listed above are here to help students get education and have plenty of scholarships available.
Colleges love seeing that you do things outside of your school walls. So Studying Abroad would be the perfect thing to show colleges that you're interested in furthering your education and that you're interested in other countries around the world. Its something that looks good on your college application but that shouldn't be the only reason you decide to study abroad.