Within Teamwork.com, you can assign a board column to a task while in List area of your project.

When creating or editing a task, select the Board Column option from the More dropdown where you can choose from your existing board columns.

Alternatively, hover over an existing task and select the board icon. You can then choose an existing board to apply to the task.

Once a board column has been assigned to a task, you will see it listed beside the task name.

Clicking the existing board column associated with the task will open a dropdown where you can change the column or remove the task from the board.

Individual task view
When viewing an individual task, you can also change the board column the task is associated with, from the task details sidebar.
If the task is already part of a board column, you will see the column listed in the left pane. Hover over the column to reveal the edit option.

A modal will open where you can then select a different column or remove the task from the board entirely.

For more information, see: Using Board View for Tasks