Specific armors are created on the "Armor, Magic" tab, rather than on the "Armor" tab where you'd be able to copy studded leather armor.
Try copying one of the existing ones that has a bonus and powers, like the breastplate of command (rather than one of those that's just a material applied to a specific suit of armor, like dwarven plate).
You'll see that the "Gizmo" button on the right-hand side is highlighted - go in there, and you'll see that it's added the mSpecMagic gizmo, and that gizmo has bootstrapped the specific armor that this is based on. You can then change that specific armor to studded leather. In the main list, you only need to set those values for things like armor bonus, armor check penalty, etc., which differ from regular studded leather armor - everything left blank will be filled in by Hero Lab by looking up the gizmo's bootstrap.
The "Cost, modified by size" field is the standard cost of the armor you're using, because that could change if this armor is purchased for an ogre. The "Cost, size-independant" is the remainder.
After that, adding the powers is handled the same way you'd add powers to a wondrous item - you'll see the standard set of user-selection options, and you'd write your script the same way you would for a wondrous item.
