The running back was traded to the AFC North side by the Philadelphia Eagles two weeks ago, having left the Dallas Cowboys as a free agent earlier this year.
The 26-year-old told the team's website: "I feel a lot better. I am more involved with the playbook now. I have a few more plays under my belt. I can play fast without thinking too much and go play my game.
"Whatever running back is out there on fire you have to continue to ride with him. Whatever helps the team out, we are going to support who is out there.
"Once you get an opportunity you have to make the best of it. That is what I plan on doing. Hopefully I have a great game and continue to go out there and have great games."
The Steelers play the Tennessee Titans in their first game of the season tomorrow.