How do I get service in France?

Has your account been open for less than 90 days? If so, you'll need to contact customer care and ask them to make an exception to add international roaming services to your account. If your account has been open for longer than that, there may be some other reason why your international services are disabled. Either way, you'll need to contact customer care. Dial 611 from your mobile device, or 1-800-331-0500 from any other device.

What plan do you have?   Did you add a roaming plan and $0 pay per use for travel?

Roaming without a travel plan is very expensive.  If you are using Gophone, you cannot roam in Europe.  

If you are on postpaid, you can login to your account, add a passport plan and $0 roaming.