My watch doesn't log any steps during bike activities. Even if it logs any steps it will be very very few steps while sitting on an indoor exercise bike so I don't really see the point.
If you mean the biking cadence, then you can use a cadence sensor. Alternatively you can wear your watch on the ankle and use a non-biking activity profile for logging the ride (i.e. Treadmill), changing it to Indoor biking later in Garmin Connect.
