To unlock Daily Challenges you have to make som progress in the story. After you have unlocked the following achievement...
...the game opens up and you can choose daily challenges (hit START and go to Challenges).
When you start the game it takes around 1.5 to 2 hours until you can start the first daily challenge. These challenges include driving in oncoming traffic, reach a specific jump distance, reach a drift score, complete autolog recommendation, .... . Nothing to difficult.