Likely you need to boil it more and cook it down. Depending on how much moisture your fresh cranberries release you may need to cook the jam a bit longer. If the jam seems too runny and isn't a jam consistency it needs to be cooked more. Continue to lightly boil the jam while stirring to keep your jam from sticking to the pan until you get the thickness you want. Once your jam is done remove your pan from the heat and transfer the jam to a heat proof jar to store in your refrigerator.