Taskfeed Board organization-wide default sharing settings are Private with Access Granted Using Hierarchies enabled by default - only the owner and team members on the Board will see the Board. 

• When Grant Access Using Hierarchies is enabled, users above the Board owner in the role hierarchy will also see their subordinates' Boards. 
  

Taskfeed Tasks are Controlled by Parent - their visibility and access are controlled by the default sharing settings in Taskfeed Lists, which are controlled by the Taskfeed Board. Therefore, in order to see other people's Tasks, you need to see the Board that contains those tasks.

How can I see my team's Boards if I'm not a member?

It is possible to extend visibility and access to the Board and its Tasks in three ways:

1. Adding Board Team Members (Read/Write)
2. Manually Sharing the Board (Read-only or Read/Write)
3. Defining Sharing Rules  (Read-only or Read/Write)

Note: You can only share Taskfeed Boards to users who have a Taskfeed licence assigned.

1. Adding Board Team Members

Board Team Members are people added to the Board through the Contributor   button on the Board itself. Contributors will be listed at the top of the Board so they can be dragged onto a Task to assign ownership.

2. Manually Sharing the Board (Salesforce Classic)

This feature is provided by Salesforce. Go to the Board record via the Taskfeed Board tab. The owner of the Board can manually share the Board to users in Salesforce or Public Groups defined by the Salesforce Admin. 

• Troubleshooting: Why can't I see the Sharing button on a Board record?
  

3. Defining Sharing Rules

Board sharing can be defined for an entire set of users in a Public Group via Taskfeed Board Sharing Rules. 

Sharing Rules are created by the Salesforce Admin and can be based on Ownership or Criteria, such as field values.