What would be a way to get saline into my sinus cavities?

A neti pot: Neti pots are available at most pharmacies. Just follow the direction on the packaging.

Sinus rinse: Niel med makes a sinus rinse kit available at pharmacies and costco. It can really help with sinus congestion and improve nasal breathing. A neti pot is another option. Make sure to follow the instructions carefully, and ask your physician if sinus rinses are a good idea for you.