The only way to join a team in Cisco Webex Teams is if a moderator adds you to it. Sometimes you'll just get added to a team because you're part of a project or department. Or, if you know about a team because someone you work with is already a member, you can ask to be added.
Reach out to your co-workers to get added to teams that they're already using. Or, start a new team to get people working together.
You can't just search to find available teams to join. Your search results only show teams that you've already joined.