Now unless you've been living under a rock, you may know that Apple have announced iOS 10 to the public yesterday, releasing it sometime in July. If however you've managed to grab the first beta of iOS 10, and want to downgrade back to iOS 9.3.2 in case either Pangu or TaiG release a jailbreak for that firmware, you can do simply by following these steps;
1.) First, head over to ipsw.me, select your iDevice from what's provided with the available firmware (right now it's 9.3.2) and download it.
2.) Wait for the download to finish (may take 10-20 minutes depending on your internet connection).
3.) Next, turn on your iDevice and plug it into your PC/ Mac using a USB cable (the computer you downloaded the fresh download on).
4.) Open up iTunes (if not opened up automatically).
5.) Click on the small phone device near the top of iTunes and hold down the SHIFT key (for PC users), or the ALT key (for Mac users) and click on the Restore button.
6.) Navigate your way to the downloaded file you downloaded in step 1/2 and double click it.
7.) It will then verify if it's an Apple firmware then wait for it to downgrade your firmware (may take about 15 mins).
(NOTE: If asked to backup, DO SO just in case anything goes wrong!)