If you are unable to see the Search for a Team tab to allow you to search for a team, you may need to enable the option for teams to be created.  
  1. Navigate to Fundraising > TeamRaiser
  2. Search for the TeamRaiser name
  3. Click Edit under the Action column
  4. Click step 4. Select Team Options
  5. Under step 2. Team Formation, mark the checkbox next to "Yes, allow teams to be created in this TeamRaiser event"
  6. Refresh the Find a Participant page to see the tab appear