The former Arsenal striker, who had been without a club since his premature exit from Wolfsburg in April, has signed a two-year deal with the Reds and is eager to quickly adjust alongside Assombalonga and the rest of the Forest squad.
The 28-year-old told the club's official website: "I think Britt and I can form a great partnership.
"It's important to complement each other well and I think we can do that. However, there are 11 players on the field who win the game and from what I've seen so far, every member of the team has done well.
"With three home wins from three and two cup victories so far this season the lads have got us into a really good spot. Now we need to continue that good start to the season and push on up the league table.
"Personally, I'm not someone who needs a lot of time to get match-fit but I will need to some to adapt to life at the club. I'll be having a fitness test in the next day or so and after that I'll be ready to go."