Only the person who created the Team Collection, the team collection administrator, can do these steps:
Share the folder that has the team collection with each team member.
This folder is typically a subfolder and its name ends with - TC.
Inform each team member when the folder has been shared and how to access it.
Then, they can join the Team Collection.
A team administrator can add another administrator.
If the folder is in Dropbox, all team members need to have Dropbox installed.
The details of how to share a folder are beyond these Bloom Helps. It also depends on if that folder is in Dropbox or on a LAN (Local Area Network).
If you will use Dropbox, here are links to help you get started:
https://www.dropbox.com/downloading
https://help.dropbox.com/files-folders/share/share-with-others