For simple forwarding to a cell phone, please see the article on how to enable forwarding from a desk phone. This process is designed for members of a Mitel workgroup and won't apply to most people.
The Mitel External Assignment feature allows you to receive incoming workgroup (and regular) calls from your desk extension on a home phone or cell phone. This setup requires the Mitel Connect Client installed on your work computer.
Please see the article on Troubleshooting Voicemail Issues for any difficulty with the way voice mail is being handled using this method.
Instructions on how to install the Mitel Connect Client
Note: Declined calls using this method will be answered by your cell phone voice mail, instead, let the call ring through to be answered by your office voice mail.
At this point, all incoming calls will route to your desk phone and all the orange status lights should change to off.