Q: How can I use wi fi hotspot in my iPhone 5s

First off, your carrier needs to support it. The Hotspot allows you to share your cellular internet with other devices. If your carrier supports hotspot, your account needs to have it activated. If all of that is in order, you would see it in Settings and be able to turn it on. From there, other devices would be able to connect to your iPhone's internet via an ad hoc network that you set up with the phone. It also provides you with a suggested passcode. See this support document. iOS: Understanding Personal Hotspot - Apple Support

First, confirm with your carrier that you have the service on your account. Then, see page 38 of the manual for additional instructions:

http://manuals.info.apple.com/MANUALS/1000/MA1565/en_US/iphone_user_guide.pdf