You don't "obtain" a licence. It's not a licence like a driver's licence that gives you permission to do something; rather, the license you apply to your software is you giving permission for other people to do something. So, just like your driver's licence is the government saying, "You have our permission to drive a car, as long as you behave in certain ways", the license you apply to your software is you saying "You, the user, have my permission to use this software, as long as you behave in certain ways."
So, all you need to do is just include the licensing statement in your software. But, as others have said, do have a look at the other licences available and make sure you understand what rights you're giving people by your choice of license.