How can i get the last parameter after slash (/) from a url

I've seen this question here multiple times, but i don't really understand where to put the code..

Let's say my website is called www.example.com.

I want to be able to get the last parameter of the url, example: https://ift.tt/2N9uOvL - i want to be able to echo 'admin'. How do i do it? And where do i put the code? Should i put the code in example.com/user?

I have not yet tried anything, but i'm ready to try.. I just don't understand where i'm supposed to put the code..