Yeah, you'll see alot of alternative stats used for aggressive actions.
In 3.5 everything was either strength or dexterity added to the attack roll, plus base attack, etc.
In 4E, your basic measure of "to hit" is your ability modifier.
With that Warlock, let's say you have a Constitution of 16 (it should be 18, since it's probably your main attack stat, depending on the build but we're saying 16), so you have a +3 modifier.
The second bonus is your level bonus. This is similar to your base attack
but it is not the same thing.
Every class adds one hald of their level rounded down to their attack rolls, whatever attribute they use. So, at first level, it'll be +0. When you reach level 2, it grows to +1.
Most attacks also add the ability mod to damage. DO NOT, however, add half your level to damage,
only to attack.
So for this example warlock a roll an attack again an enemy with a Will defense of, let's say, 15, you would roll as follows:
Attack roll
Rolling 1d20+3:
(13)+3: Total = 16
Damage
Rolling 1d6+3:
(1)+3: Total = 4