I saw that there was a new car pass released this month. I searched in Forza 5 itself, but can’t find it. Can someone help me buying it?
You mean the February Smoking Tires car pack, right?
Not the Car Pass (which is the Season Pass of this game).
By now, when you start Forza 5 there should be a prompt that it needs to update.
Do that and you should be able to see the cars in the dealership and buy the car pack from there.