In Activy, the team creation process is really simple :) However, remember that not every challenge allows team creation by users. Information on that can always be checked in the "Rules" tab in the competition panel.
1. Enter your company's contest and choose one of the categories in Group tab
2. In the upper menu you will find the button "Create a team"
3. Click it, and the application will redirect you to a screen where you will have to enter the name of your team (for example: department, team) and an optional password (use this option if you do not want someone from another team to interfere in your team's doings)
4. Your team will appear in the ranking within a few seconds