The Bible doesn’t tell us. ArkenCounter.com notes: He may have already been experienced in shipbuilding, or he may have worked to acquire this skill after God called him to build the Ark. Whatever the case, we are confident that God made sure Noah was properly equipped to complete the task.
The Bible, in Genesis 5–9, gives us the bulk of what we know about Noah and his life. Noah was married and had three sons: Shem, Ham, and Japheth. Each of the sons had his own wife.
In the years Noah spent building the Ark, his grandfather Methuselah and father Lamech were alive and may have even assisted Noah in some ways. We are told that Noah walked with the Lord and found grace in His sight (Genesis 6:8–9; cf. Ezekiel 14:14, 20).
See AnswersInGenesis.org's What We Know of Noah and the Ark in the Bible to learn more.
Of interest, RealTruth.org shed a light on what was it really like before the flood.