The 23-year-old agreed a six-month loan deal on transfer deadline day as Sunderland look to get him off their books in the coming months.
Watford will have the option to sign him permanently in the summer and Ndong wants to earn another contract at a Premier League club.
He made 21 appearances in the Championship for Sunderland before his move to Vicarage Road and is confident he has the ability to compete in the top flight.
Ndong told the club's official website: 'My aim for the six months until the end of the season is to be the best I can, to give everything and to show the club I am capable and to give them confidence to sign me in the summer.
'It's a good chance to come back to the Premier League, it's a chance for me to express myself and show everyone what I can do. The Premier League is a big league, you find the best players and managers in the world there. It's got a lot of exposure as well.
'I'm hoping that this loan goes well and that they take the option for me to sign.
'I'll have to work hard to convince the coach and all the staff what I'm capable of and hope everything goes well here, like it did at Sunderland, even if it was difficult at the end and I'm grateful always for the chance given to me.
'Sunderland was the club that let me be in the Premier League and gave me the chance to be known in England. The club decided this was the place for me to progress and that's why they let me come to Watford.'