Go to Jobs, click on the selected one, go to the Post a job tab and use the red button in the right, bottom side:
Go through the next 4 steps to create a job post, that include:
choosing the job post template or creating the job post manually,
deciding on the list of consents,
choosing the application form template or creating an application form manually,
posting the job on Career site, job boards and social media (not required).
If you decide to use a job post template, you will have to confirm your choice to go further: