Now, in #54 we find he was sent to the "best" private school specifically because of his habit of jumping off things, where he did well at sports, academics, and gets bullied for the size of his shoulder blades. One day he notices a suspicious feather on his bed and then quickly realises he has... wings! He's worried about being found out, and he's rich and secure enough that making himself unpopular seems like a viable option.
One day there's a fire at the school, and he evacuates through the window, discovering he can fly. He realises that there are others to save, and gets them - first dressing up in an Angel costume scavenged from the school theatre's storeroom.
There's a little bit of a disconnect between that last panel of the first part, where Angel's schoolmates vow to find out who the mysterious Angel figure was, and the next issue, which sees Angel having left the academy (or possibly just on summer break), and having set himself up as an independent superhero, the Avenging Angel. He's trying to make a name for himself, but it's rotten luck when one of the criminals he foils is a "known liar" and not believed.
Meanwhile, the X-Men have detected a new mutant. A good mutant or an evil mutant? In a surprising acknowledgement of moral complexity, Xavier says "we do not live in a world of lucid blacks and whites, Bobby... [...] Right now, whether that mutant we've located uses his power for good or evil may well depend on us". The X-Men (being Scott and Bobby) turn up and try to recruit him, and exhibiting all the people skills we've come to expect from them rapidly get in a fight with him. After learning the value of teamwork, he signs up. His moral choice was never in any real doubt - his brief wonkiness was simply result of technobabble. Warren has had as far as we know no traumatic "with great power comes great responsibility" moment, he just got powers one day and then decided to help people because that's the right thing to do. Truly an Angel.