I would scrape branches in areas that you think are dead to ensure they are not green underneath. Confirm the dead branches and cut them out so they can be filled in with new growth. Also, if they snap easily it's generally a safe bet it is dead.

Removing large dead branches isn't ideal because it can give the plant a funny look for some time, but it will fill in with fertilizer and water especially. In most cases, better off to just get it over with if it's truly dead.

One additional, but more drastic approach is if it was newly planted, you could dig it up and turn the new face of the plant where you want it, hiding the bare spots a bit. Keep in mind if you do this, watering needs increase.

Either way, turning some compost in the surround soil is always a good idea as well!