There's no strict process for creating a personal mission statement, but it usually starts with taking some time to yourself to think about what you care about most, and who you want to be.
Once you have a rough sense of the content you want to put in your statement, you can start to create it, whether in straightforward writing, or one of the weirder methods we mentioned before.
If you're struggling with getting started on yours, you can search online, or simply swipe up to find plenty of examples of others' mission statements.