i want to upgrade my iphone 4s from ios7.1.2. to ios 10 and i dont know how

The iPhone 4 can not be upgraded beyond 7.1.2.

The iPhone 4S can not be upgraded beyond 9.3.5.

Are you sure it is a 4s?

Check to be sure:

Identify your iPhone model - Apple Support

https://support.apple.com/en-us/HT204204

Please verify the model number at: Settings - General - About - Model = ???

How can I upgrade my iPhone 4s

Please read solution posted above.

You know if you read the thread it will keep you from posting silly questions.

I want to upgrade my iPhone 4s please how can I do it please

Repeating yourself only makes you look stupid.