How to change lock-screen icon layout on my MacBook?

So I keep trying to look up how to change the icon when you open your computer and it has a little circle with a picture above your name but everything is telling me to go to users & groups and change it there but that just changes my Apple ID icon which is not what I am trying to change because doing that does not change the icon on my Lock Screen and nothing is telling me any different information please help!

[Re-Titled by Moderator]