Until is open keep it in a dry place as long temperature is around 20 to 23c. once you opened the package
1 - no need to store again because the big racoon took it and eat it (my preferred excuse)
2 - if any left keep it in the fridge's door at the top where temperature is not so cold if uneaten for several days.
3 - If you plan to finish it in the next few days then no need for fridge.
What you don't want to do is have the chocolate melting and then put it in the fridge, depending on the cocoa content the elements will split and you have lumps of butter and sugar separated from the cocoa.
The solution for this, melt the chocolate in low eat, mix it thoroughly and put it in the ice cubes tray, let it set and eat it