The stationary bike is a good choice for a cardio workout if you're just getting started with exercise and is a great way to ease into cardio. In fact, you get the same cardio benefits as when using the treadmill or elliptical trainer or when walking or running outside.
Real talk: this is gonna be hard. Indoor cycling classes are high intensity and fast-paced, and even the most seasoned fitties can struggle during their first session.
Beginner is usually on an 8x8 or 9x9 board containing 10 mines, Intermediate is usually on a 16x16 board with 40 mines and expert is usually on a 30x16 board with 99 mines, however there is usually an option to customise board size and mine count.