Login to the portal (portal.via.co.uk) and within the top right, click on the down arrow to change the status, as shown below:
An alternative way is to access the menu by dialling the following codes from your Skype for business client or handset.
Logging in Menu:
*0 - This will take you to the full menu
Below shows you the direct shortcuts to the menu:
*1- Log In/Log Out to Call Queue
*4- Finish Wrap up (This option is only available when an agent is in Wrap Up)
*5- To Extend Wrap up (This option is only available when an agent is in Wrap Up)