When you create a new Job, you’ll associate this with a “Company.” Simply type your Company name in the drop down - if it already exists on Behance (you might be a member of it or not, either way is fine), you’ll select it. If you don’t see it, click the option to create the Team.
Team pages are a home for your company - you can choose to use your page to showcase work, or to simply aggregate any open positions you have, which will happen automatically. This profile will make it easier for the right creative to discover opportunities at your company, so associating your Job with a Team Page is required.