You can indicate whether an interval should be done seated or standing when designing your workout. As a default, all intervals are seated when added to your workout, since this is the most commonly used position when riding a bike, indoor or outdoor.
Here is a video that will show you how to add seated/standing position
Double-click the top half of any interval to indicate the interval should be done standing up.
A black line will appear at the very top of the interval in question to indicate graphically that the interval should be done standing up. To remove it, simply double-click the top half of the interval once more.