Always use fresh if you can. Nothing beats the taste impact of fresh herbs. If you do not have fresh herbs, you can use dried however, you must divide by 3.
The recipes contained on this site always assume fresh. If the recipe calls for a tablespoon of fresh thyme for example, and you only have dried thyme, divide the volume by 3. So, instead of a tablespoon of fresh thyme you would use a teaspoon of dried thyme in the example. (Yes my friends, math matters.)
Lastly, spices and herbs have a shelf life though most home cooks seem to ignore that. We have been in friends and family kitchens cooking and open up their spice cabinet to find items several years old. We suggest you only utilize spices and herbs dated within the last 6 months. Some people advise you to assume a one year shelf life but they are wrong! We’ve tasted and tested the differences and 6 months should be your time limit for throwing out the old stuff.
Remember, fresh is always best, and the fresher the better!