Changing SSH Port

Hello Great Ones

As you know the default for the SSH is to use port 22

I want to change the port to 123 (only example)

I tried to change it in the config fle but it would not let me save the file/

My questions are:

How do I change the port connection when i try to use ssh to 123 and not 22?

I am sure I need to edit a file but which one and how do I find the right file to edit?

Thanks for all your help