it sounds to me like you just have the bare roots in a bag of some sort, these should be planted right away because a hard frost will damage the bare roots. (If that is what you have)
Watering is pretty simple and their are no explicit instructions for watering any plant (as far as water so many times a week and what not). Just dig the soil around the roots a little with a spade or small shovel and if the soil is dry then give the plants a good, long soak with sprinkler or soaker hose.
There are two paradigms of thought about when it is best to water plants:
1) Do not water at night or in early morning because if you do, you will encourage diseases such as damping off and other fungal/bacterial growths. Therefore, water during the day, late morning being the very earliest.
2) Water at night and in early morning so as to allow the water to soak into the soil before it evaporates. The caviat (sp?) to this techniqe (that I use) is that you need to have healthy, well balanced soil and not use herbicides and pesticides that really just select for resistant organisms and kill both beneficial and pathogenic organisms.
Anyway, this method allows the water to soak deep into the soil and allows the roots of plants (including grapes) to grow deep into the soil in search of water and nutrients.
For a fertilizer for you grapes, I have found that liquid fish fertilzer works best. Also, when you plant your grapes add a handful or two of Kelp Meal to the holes before placing the root balls in the holes. I wouldn't recommend planting them in pots because of the fact that in winter; they are prone to freezing and also a pot is a closed system and plants tend to grow better and are generally more healthy in an open system.
Futhermore, in the soil; your grapes will be less prone to dessication and various plant diseases(provided that you have a healthy soil).
There are a lot of threads on how to create and maintain healthy soil in the forums and on the website so, I encourage you to look at those as well.