They are already present under the appropriate workout category and are distinguished by the blue shopping cart icon and the Uplay Unit cost at the top.
It can be found under Workouts then Toning.
Before it is unlocked, it will show the blue shopping cart icon and the price of 30 U.
Once redeemed, it will be found in the same location, but will be unlocked and ready for play.
The other Uplay Rewards can be found in the destinations below.
Workouts / Legs / Legs: Shape and Burn (F)
Workouts / Sports Preparation / Soccer: Power and Strength