First Contact been Humanity and the NorAellians happened when a NorAellian science vessel made contacted with the failing Perseverance Fleet. In an effort to help the in danger humans, the NorAellians helped them establish Calysto and The League of Allied Worlds.
When the NorAellians first discovered Humanity they were very taken back by the rudimentary state of their technology. They, at first, thought they'd discovered a colony of Sooni. However, they stayed in the shadows and kept watching, eventually realizing the truth: the Sooni were modified Humans, and this world was the true origin of the race.
From that point onward, the NorAellians continued to observe Humanity without interfering for at least a thousand years prior to the launch of the Perseverance Fleet.
As a rule, the NorAellians had no intention of interfering in the politics of Humanity, including their wars. However, once the Perseverance Fleet launched, they felt it was a fascinating chance to watch a pre-subspace society attempt to colonize another star system; something they'd never even heard of a race attempting before.
Given how rushed and ramshackle the fleet was, it was impressive that it lasted fifty years. However, that was about the limit of how far the fleet was going to make it. One of the ships had completely failed, being scavenged for parts for the other two, and the population was on the verge of starving. Health was poor, and it was clear the venture was going to fail without some sort of miracle.
The NorAellians decided to interfere. The fleet had been considered lost by the rest of Humanity; there didn't seem to be a reason to let these humans die. So, they initiated contact with the fleet and after a suitable amount of confusion and concern from the huamns, they offered health services, food and some support.
There is a pervasive story that is told about this moment in human history. The story, as it goes, is that when the humans learned that the NorAellians had the ability to travel faster than the speed of light they asked if the NorAellians would transport them to a colony world. The NorAellians said that they had already interfered more than they had intended to. However, the fleet captain had a box of comic books. When he showed them to the NorAellian captain, the concept of recording knowledge in illustrated form like that impressed them so much that in exchange for the entire box of comics, the NorAellian agreed to simply give them subspace technology.
In reality, the NorAellians claim they offered to transport the humans without needing to be convinced. There was definitely a 'cultural exchange' that included a box of comic books, but the NorAellians downplay the importance of the comics.
The NorAellian version is almost assuredly not completely true. There is debate which version is the most accurate, but it is most likely a combination of the two.
The NorAellians both helped the colonists and established trade with them. Because the new Calysto colony was in such need, the NorAellians helped them with dozens of crisis in the first few years. In the end, they ended up giving The League a massive amount of technology and a huge technological leap forward.