Well how can the websites we build be available on the internet.Can some help me with that

Answer 1

Yes, you need to buy a domain name and assossiate it to the ip of your choice (your server ip).

Answer 2

I think we need to buy permission.....isn't it

Answer 3

So how do I do it now

Answer 4

First you need to find a domain name registrar. They can even host your server if you want.
https://en.m.wikipedia.org/wiki/Domain_name_registrar