As a student there are likely many times in which you have thought about seeking assistance from one of your professors, yet have failed to do so for a variety of reasons (fear of being seen as "stupid", anxiety over having missed several class periods, nervousness about not knowing what to expect, or feeling uncomfortable talking with an authority figure).
Whatever the reason, you are not alone. You can learn how to approach a professor for help.
Prior to meeting with your professor, have a clear idea of your purpose.
Once you have identified the specific reason(s) you need or want to speak with your professor, determine how quickly to do so.
Arrive prepared with your list of why you need to approach your professor for help. Any anxiety you may experience can be lessened if you are organized beforehand.