Login to the SD Elements application with you credentials and go to Password settings as shown in the image below.
Once you goto the Password Settings page
Please enter your current password and the new password in the respective fields.
You will be asked to enter a security question, after this is done click on the "Update Password Settings" button at the bottom right of the page to complete the password reset.
If you happen to lock yourself out of firstname.lastname@example.org account accidentally, or you forgot the password for it, you can reset the password from Command line.
You can change the password by running the following command:
sde manage_django changepassword email@example.com
NOTE: In new deployments, you need to run that with sde_admin user, e.g. by adding sudo -u sde_admin before the command.
The newly reset password can be used to login to the web interface.