How did Nathaniel become a disciple of Jesus?

he was holy

Philip (Nathanael's friend or his brother) told Nathanael that he (Philip) and his friends had found this guy down by the lake who seemed to be the Messiah promised in the Bible. Philip asked Nathanael to come and see. While he approached Jesus, the following exchange occurred:

St. John 1:47-50

47Jesus saw Nathanael coming to him, and saith of him, Behold an Israelite indeed, in whom is no guile!

48Nathanael saith unto him, Whence knowest thou me? Jesus answered and said unto him, Before that Philip called thee, when thou wast under the fig tree, I saw thee.

49Nathanael answered and saith unto him, Rabbi, thou art the Son of God; thou art the King of Israel.

50Jesus answered and said unto him, Because I said unto thee, I saw thee under the fig tree, believest thou? thou shalt see greater things than these.

51And he saith unto him, Verily, verily, I say unto you, Hereafter ye shall see heaven open, and the angels of God ascending and descending upon the Son of man.

It was enough to entice Nathanael to accompany Jesus and become His disciple.