How can I use my phone in Europe what do I need

Turn on roaming....?

First, that depends on what model phone you have. Then, it goes into what your wanting to be able to do, with your phone, out of the country. Depending on your needs you may want to consider adding an international plan. Unfortunately, your question doesn't have a straight forward easy answer. My best advice would either be to call customer service or go into the store. I know this isn't the answer you were looking for but hope it helped in some way. Good Luck.🙂