You can add water to the pan when cooking a turkey in the oven but it's not recommended to add any water to the pan to cook the turkey.
If you do add water to the turkey pan it can cause the turkey to become steam burnt and it's best to just place the turkey into the turkey pan and bake the turkey without any water.
When you do cook a turkey in the oven set the oven to 350 F and cook the turkey for 20 minutes for each lb of the turkey.
Most turkeys will be fully cooked after 4 to 5 hours depending on the size of the turkey and when you stick a meat thermometer into the middle of the turkey and the temperature of the turkey reaches 165 F then it's done.
When the turkey is done you should allow it to rest for 30 to 45 minutes to allow the turkey to absorb the juices that came out of the turkey during the baking process.
The resting of the turkey will make the turkey more juicy and not dry.