There is apparently some amount of confusion on how combat works in the game. I apologize for this and will try to explain it more succinctly.
The number of dice rolled is listed on the weapon on the faction sheet.
Roll the dice listed. For instance, Grandpa's shot gun does 3d6. Roll 3d6 and compare the dice rolled individually to the target's Hit Me score.
For every rolled number at or above the targets Hit Me score, they take a wound unless they are in cover, in which case their Hit Me score is increased by one to max of 6.
Therefore each die has the potential to cause a single wound.
There is no roll to hit then roll to wound and dice are not added together.
I hope this helps.