Nasal rinse bottles can be useful for people who have sinus problems. Please consult your doctor to find out if this is the right thing for you. Seeing how other people use the bottle is helpful when you start using it.
This link will take you to a youtube clip showing one brand of rinse bottle. Smelltraining.co.uk does not endorse this brand, but this clip is well done and explains in detail the function of nasal rinsing.