You can order any human settler to do any task they ought to be able to do (children will only be able to do hauling and non-toolrequiring gathering). If your adult settlers need a tool for a task, they go and get one. Normally.
By right-clicking on the ground they move there (double clicking makes them run).
With the same method you can make them pick up items (children won’t haul logs or stone).
A successful assignment will be highlight the task icon or building outline in green. Task, that can’t be assigned – or the right tools aren’t carried with them – will highlight in red. See further behaviour above.