When using HSS are you allowed to make attacks at more than 1 character if you have 2 or more

If you are asking if a figure with can target two figures when he makes his ranged attack, yes. If you are asking if he can make two separate attacks, no.

So anytime a ranged combat ATTACK is given not an action you can use the multiple bolts?

Because HSS allows you to make a close or ranged combat attack, you can target as many characters as you have bolts.

Yes, you don't need to take a ranged combat action to use the extra bolts.

basically yes. There are some specific powers that limit you to one target but for a "vanilla" ranged attack you can target as many figures as are in range and LOF, up to the number of bolts.

You don't give an attack. You make an attack. The number of s is simply the number of opposing characters an attacker can target regardless of how it came to be making a ranged combat attack (vanilla ranged combat action, HSS, whatever), barring any restrictions (such as with RCE)