You can change your password by logging into the UI, click your helmet at the top right of the screen, click Account, then Change Password.
You can also do this on members.iracing.com from a supported web browser (Firefox, Chrome, Edge) and go to Account...My Account.
On the My Account Home page, click Change Password
In the first fields, type in your current password.
In the next two fields, type in what you want to change your password to
Then click the blue Change Password button.
You should now see the message: Your Password was updated successfully.