I agree with Legacy123 in that more details are needed before we can give you a good answer.
What OS are you using on your VPS? Do you currently have anything besides the OS installed on your VPS? Do you know how to use command line? What do you plan to do with your VPS?
I also agree with Legacy123 that using a web based interface / GUI such as the free
Webmin is one of the easiest ways of managing a VPS including mail functions. You may also want to consider the Virtualmin add-on for Webmin after you have installed and are comfortable with Webmin. I use both on my own VPS. If you decide to you Webmin and / or Virtualmin read all available information at the website before installing - this will save you a lot of time and headaches.
Good Luck
Carl