You change the prompt by changing the value of the PS1 shell variable. You can look up all the options for it by looking at the man page for bash (man bash). Other shells use a different variable, but there will be a corresponding variable.
Assuming you're using the bash shell, you can edit two files to get what you want:
Editing ~/.bashrc will be a personal change. That is, only you will be affected. Setting the value in this file overrides the global default.
Editing /etc/bashrc will make the change the global default. Every user will have the new-style prompt unless they have explicitly defined something else in their own ~/.bashrc file (as described above).