While each school has its own set of requirements, there are certain minimum requirements for admission. An IB diploma meets their requirements, as does one year of college credit. US students can meet the requirement with three AP scores of 3 or higher. International requirements can be found here. Students from non-anglophone countries must demonstrate English proficiency through IELTS or TOEFL scores and all applicants must submit a copy of their passport.
The Danish application is called the Coordinated Enrollment System or "KOT". Students can apply to up to 8 programs or apply to all the schools in the country. When you apply, you rank the schools in order of preference when you apply. If you qualify for more than one, you get your highest choice pick. You won’t be accepted at more than one. The application deadline is March 15th for non-EU students. You should hear back by June 1st.