You can create teams from the "Activity" page. Click on "Activity" at the top left, or visit this link:
Next, click on your team name, which should appear to the left of the screen, directly above the first visible avatar and team updates. You'll see a drop-down menu. There should be several grayed-out options, which are common team selections such as "Business," and blue text that reads "Add a Team."
You can select any of the gray text to create a team with that name, or click on "Add a Team," and type in your own name choice.
You can invite coworkers to this team, and they can join individually.