By default your calendar is shared to the users of your organization with view rights, meaning they can see the public events on your calendar but can't make any changes to the calendar. You can share your calendar calendar to other users if they need to be able to make changes to your calendar:
- On the calendar page hover your mouse over the calendar you want to share on the left side of the page
- Click on the three dots that appear when hovering the mouse over the calendar and click Settings and sharing
- Scroll down to "Share with specific people" and click Add people
- Add all the users you want to share the calendar to and choose the access level by clicking Permission
- Click Send
- Calendar is now shared to those users. You can change the permissions afterwards from the box on the right of the user or remove it by clicking the X next to the user
