Tasks may not be visible on your Task Board for a number of reasons - Most likely they are either in your backlog, hidden by a filter or haven't been assigned task properties yet.
Backlog/Needs Action
If a task has a "backlog" status against it, it will be visible on your board if you expand the Backlog list - from here the tasks can be dragged from the list and dropped into another list in your board to update the status. This is lnown as "Needs Action" in new projects.
The Backlog list can be shown by clicking the backlog icon 
in the top left corner of the Task Board screen.
Filters
The tasks displayed in your Task Board can be hidden from view by applying a filter. If you can't see a task you've created on the board, it could be that it's hidden from view by a filter.
You can tell at a glance if a filter has been applied to your Task Board by viewing the status of the icon in the top right corner:
Clicking the Filter icon will open an options menu, from which you can switch off individual filters or clear all applied filters from the board.
Branches Don't Have Task Properties
If you use the Map area to brainstorm ideas, you may have a lot of branches that you're now ready to start managing as tasks.
If these branches don't have task properties applied to them though, then they won't appear in your Tasks area.
The good news is that you don't need to jump back and forth between the Map and the Task Board to add these branches as tasks though.
Expanding the Explorer section in the Task Board will let you browse a list of all the branches in your selected Map (either the main project map or supporting Documents area maps)
To add these branches to the Task Board to start managing them as tasks, just drag and drop them from the Explorer onto the board.
