Introduction
In Preferences, go to the Calls tab and check the button next to "Turn on call forwarding".
Instructions
1) In your Mac's menu bar, click Skype for Business. Then, click Preferences.
2) From the the Calls tab, check the box next to "Turn on call forwarding".
NOTE: The radio button next to "Forward my calls to" should be selected by default. If not, select it.
3) Click the drop-down menu next to "Forward my calls to". Then, choose the option you prefer.
Outcome
You have now set up Skype for Business to forward incoming calls.
TIP: For call forwarding to work, Skype for Business does not need to remain open and your computer does not need to remain powered on. Call forwarding settings are stored on the TTU Unified Communications servers.