To Complete The Forza 6 Achievement Takin A Spin you need to take a car or Forza 5 for a test drive, There are 2 ways to complete the Takin A Spin Achievement, You Can Either select Test Drive From The Go Race Menu In The Forza 6 Menu And you will go for a test drive in your current car or you Can select Test Drive When your finishing Modding Your Car.
Once You Have completed 1 Lap press start and then quit and then the Forza 6 achievement Takin A Spin Achievement will pop on the screen and your done.