You did almost everything right. Here is how it works.
First, the two characters are two individual units, and must be treated as such. Both characters get to fire overwatch, both were charged. In order to make a successful charge (only one charge roll is done per unit), and only one wraith needs to get within 1" of either character (because the wraith charged both characters).
The rest of the wraith can move where ever they want to, but need to stay within unit coherency. Its important not to move within base contact when charging. After a successful charge the wraith unit gets picked to fight, they pile in, which means they can move 3" (this is optional), but when they move, they must move towards the closest enemy model, this is on a model to model basis.
The wraith can use this move to get every model as close as possible to either characters, but still not in base contact. Now they get to attack the characters. To target an enemy unit, the attacking model must either be within 1" of that unit, or within 1" of another model from its own unit that is itself within 1" of that enemy unit.
This means one wraith within 1" of the battle leader, and another wraith right behind that wraith can attack the leader. If the wraith in front is within 1" of both character it can attack both characters, same with the wraith behind it. After fighting the wraith get to consolidate, which is another 3" move, again moving towards the closest enemy model. This is optional. If pile in and consolidate is done correctly its possible to completely surround both characters, making it impossible for them to fall back out of melee. After the wraith completed the fight phase the characters get to fight back, if they are still alive.
There are plenty of videos about the charge and fight phase on youtube. I suggest watching learning how to play warhammer
40k 8th edition from miniwargaming, its a good start for beginners, there are more episodes, this one is charge and fight phase :
https://www.youtube.com/watch?v=MlnSqRHnTlI
There are more videos from D6Evolution on youtube for more advanced tactics in the charge and fight phase.