How to re-attach gutter to house

There are some kinda big twisted nails that seem to hold the gutter - or some type of gutter hanging hardware, to the house. recent heavy rains seem to have forced a section of the gutter to come loose form the house. i have done some DIY projects but admit to being ignorant of how gutters are hung or the best way to re-attach the guttering. I fear the wood is now just not in good enough condition to just hammer the nails back in - plus, I can't see a practical way to hammer the nails.

any guides or advice to parts/techniques to put my gutter back?