Most sinus infections are non bacterial which require no antibiotics to treat and those non bacterial sinus infections will usually go away on their own without treatment within 1 to 2 weeks.
When you have a sinus infection you can use a Neti Pot to clean out your nasal passages and drink plenty of water to stay hydrated.
You should also use a humidifier or take a steamy shower to help with the sinus infection.
If the sinus infection lasts longer than a couple weeks then it could be a bacterial sinus infection which would then require antibiotics to treat properly.
If you take antibiotics the sinus infection should only last around 3 to 4 days and you should begin feeling better.