Go to Settings, by clicking on the settings icon on the left green bar.

Click on the "Workflow"

Find the "Risk Workflow"

Edit it by clicking on the three bars on the right hand side

Now you see the following screen, where you can rename existing statuses or add new status for your risk workflow.

Is it possible to change the workflow attached to my board.
You can edit the statuses of your workflow linked to the board, however you can't change the association between board and the workflow scheme that you selected at the time of creating the board.