No, you don't need a special App. You can text people using the same number you call use for a normal phone call, and the same way wherever you are starting from, as long as you include the country code.
- First you need to dial the prefix to signal it is international call. From Europe it is "00", that is why the number you were given starts "00". From the US the prefix is "011" (I think). From a mobile phone it is + (yes, the plus sign).
- Then the country code for France: 33
- There are no area codes in France, all numbers are 10 digits starting with a 0. When dialling from a different country, you drop the "0" and replace it with "+33".
So, from a mobile phone (anywhere): + 33 {9 digits}
From landline in most European countries: 00 33 {9 digits}
From landline in the USA: 011 33 {9 digits}
If you don't believe me, it is all in Wikipedia here: https://en.wikipedia.org/wiki/Telephone_numbers_in_France