Create your project board in the same workspace as the Portfolio board. Boards in different workspaces can still be connected, but keeping them together makes them easier for your team to find.
In the same workspace as the Portfolio board, click + Add in the left sidebar
Select New Board
Name it using your team's convention, e.g. "[Your Name] — [Project Name]"
Choose Main Table as the board type
Click Create Board
Naming matters
A clear, consistent board name makes it much easier to find and connect to later — both for you and for whoever is scanning the Portfolio board.