Muslims beleive that Muhammad became a messenger of God. How did that happen?

In 610 when Mohammed was 40 years old he had his first revelation in Mecca. The revelation came from the Angle Gabriel. Mohammed continued to receive revelations for the next 23 years. They were told orally and when they were written and completed in 650 these revelations are the Koran. Muslims believe that Mohammed was the last messenger of God as well as the prophet of God. They do not believe that Islam is a new religion but the continuation of the faith of Adam, Abraham and others.