can you let me download the update

You do not mention which iPhone you have and what its current iOS is. In general, to update an iPhone, you select Settings > General > Software Update. At that point, if your phone is eligible for an update, you will be prompted to do so. If this does not work for you, please provide more detail, including:

• Which iPhone do you have? To find out, select Settings > General > About. Look for Model Name. 
• What is its iOS? To see this, select Settings > General > Software Update. That screen will identify your iOS version. 
• What happens when you try to update?