In any job, go to the Posting tab, search for Seek in the jobboards, and press Connect, then Edit on the division you want to set up.
This email template will appear, click Send Request:
Seek will then process your request and send you the Seek Hire Id. You will then come back to edit the Seek connection settings, and paste it in the field below:
Save, and your account will be connected and you will be able to post to Seek from any job.
Note: if you have multiple divisions, you will either need to set this up for each of them individually, or select "Use Parent" as the account to post into: