There's some default text above the new job post form that looks something like this:
Fill your position, fast.
Get your job posting seen by job seekers.
30 days for free
You have full control over this content. To change it:
Go to Pages
Click Manage page next to Checkout page
Add/update the content in the text editor
Click Update page when you're done
You can also edit the meta title and meta description for this page which can improve your SEO.