A lot of that depends.
First, you'd need to have the SHSH blobs.
Second, you'd need to be jailbroken. Only possible on certain firmwares.
Third, it would need to be possible for your device (which you did not mention) and therefore have a tool to do it.
If you have no idea what blobs are then I can guarantee you don't have them - in which case the entire chain breaks down. Your best bet at that point is to find a device with iOS 10 on it and buy it.
Anyway, I'm not sure even with blobs it's possible at this time.