Q: I am using iphone 4s but the personal hotspot option is not available in my phone, please help how to make this option available ?

Try the usual steps: restart, reset, restore.

http://support.apple.com/kb/HT1430

http://support.apple.com/kb/HT1414

If restoring using a backup doesn't help, try restoring the iPhone to factory settings and try for a while with just the Apple-included apps, to make sure it's not an issue with a third-party app. If it still has problems, it may have a hardware problem and will need to be sent to Apple.

Contact your carrier. Ask if they offer that option and subscribe to it if they do.

hotspot will always be in the settings weather or not its available on the carrier. It's a matter of getting it to work, which is what the data plan has to have

It doesn't show in the top level of settings until it has been provisioned by the carrier, as I recall. At any rate, it's unclear from the original post just what the problem is. The OP did not specify that they couldn't find it in the settings. And, in order for the personal hotspot to work, it must be provisioned, so if they haven't done that, they need to.

I would say that both of our posts contain useful and necessary information.