Answer:
first of all people who want to become Muslim have to repeat the lslamic testimony of faith(The Shahada).
The Shahada is:
"ASH-HADU ANLA ELAHA ILLA-ALLAH WA ASH-HADU ANNA MOHAMMADAN ABDUHU WA RASULUHU".
(The English translation is:
"I testify that there is none worthy of worship except God, and I testify that Muhammad is the messenger of God.")
later they have to obey the Kur'an-i Kerim(Holy Qur'an) and the commands of the Prophet Mohammad.