You can use either. Fresh ube tastes much better, but frozen ube will work very well too! The only time I would recommend adding ube extract is if you use frozen ube. This will enhance the flavor.   Make sure to thaw the frozen ube so that it'll be easier to heat and cook it in the recipe.  Frozen ube may add a little extra moisture, which can extend the cook time. If you keep an eye on the texture, you will be fine.  Fresh ube can be steamed and grated and used as per the recipe.