The Switzerland winger arrived at the City Ground yesterday from Bologna.
Ndoye told Forest's website: “I’m really happy and excited to start with the team and play in this beautiful stadium. I’m grateful to be at such a historic Club like Nottingham Forest.
“Every decision that I take, I take it with my family and we have spoken a lot about what is best for me and we were all in agreement that Forest was the best. They are really proud, just as I am to have them here with me.
“One of my dreams has always been to play in the Premier League. I had a good season last season and I think it’s the best time to arrive in this league.
“The Forest project is so ambitious, just as I am. It was the perfect moment for me to progress my career and come here.
“I saw the great season the Club had last season and I want to bring my qualities to the team and to continue being ambitious with this Club.
“I can’t wait to meet my new teammates, the coach and start to work towards a great season."
Premier League is the best of the best
Ndoye also said, “The Premier League is the best of the best and there isn’t one easy match in this league. You need to be at the top level every week and every match which is another big reason why I came here.
“I want to progress and improve my qualities and I know this is the best place to do that.
“To play with European football back at the City Ground is going to be special, I’m just so excited to start, to see the fans and hopefully score some goals here.
“My best qualities are my speed, my dribbling, I like to go one-v-one, score some goals, assist my teammates and work with the team to win each match. I will give my very best for this shirt.
“Even without the crowd you can feel what will come in the stadium. I can’t wait to see it full and to play in front of the fans.”