The question is just as simple as it sounds.
Would it tuck them under like a bird? make running motions like it does when running on the ground? some other movement that actually aids in flight somehow (if so, what is it?)
Assume the standard trope Pegasus, an otherwise normal horse with the exception of the added wings.
I can't think of any reason why a rider would change the answer, but if it does, please explain the difference and why there's a difference.
To address the concern regarding the method of flight (magic vs physics), I've never seen any depiction of any 'standard trope" Pegasus with large enough wings to power it's flight through natural physics alone, so magic definitely comes in to play, but the fact that it has wings at all means physics is also involved. Use best judgement when deciding just how much of each is involved, and adjust answers accordingly.
The question was originally conceived as a bio-mechanics question, related to how the musculoskeletal system of such an animal might cause the wing motions to interact with the leg motions while in flight. But, since other considerations could certainly affect how the animal might behave, the overall question isn't specifically aimed at any single particular aspect of either flight or biology. Instead, if answerers feel that aerodynamics requirements, or any other aspect I haven't considered, would cause the animal to intentionally suppress what would otherwise be the most natural musculoskeletal motion to gain aerodynamic advantage, or vice versa, that's fine. Best answers should provide science-based explanation of why one aspect dominates any others, and causes the motion described by the answerer.