There is no option in Box 15 for Puerto Rico because Puerto Rico is not a state. It is a US possession.
TurboTax does not support filing of Puerto Rico returns. You can get Puerto Rico Form 482 at Departamento de Hacienda.
How you file for Puerto Rico depends on whether you are a “bona fide” or “non bona fide” resident of Puerto Rico, based on how much time you spent in PR and whether you had permanent residence there.
For more info see Topic No. 901 Is a Person With Income From Puerto Rico Required to File a U.S. Federal Income Tax Return?