If you have not connected with a school, then you will not be able to post jobs.
After a school approves your connection, you will be able to submit job postings to that school's community.
To start this process, visit the My Schools section of the platform (link in left-hand side navigational menu) so you can request access to the school that you would like to post jobs to.
Scroll down until you see the "Select Your One Free School" drop-down. From there you can select a state, browse the schools, and submit a request to connect with the school of your choice for free.
You can submit job posts to that pending school connection while you wait approval. Those job postings will appear in the "unconnected" section of My Jobs. Once that school approves your connection, the post will move into the school's pending queue to approve and will appear in the "submitted" section. When approved by the school, it will appear in the "published" section.