You could:
* Use the name as it is: "Shania" is perfectly understandable in French.
* Phonetically approximate it: "Chania" is a pronunciation that's close to the English pronunciation.
* Choose a French name with a similar meaning: If "Shania" has a special meaning to you, you might look for a French name with a similar meaning. For example, if it means "beautiful," you could consider "Belle" or "Jolie."
It ultimately depends on the context and what you're trying to achieve.