Markdevoll,
Yes you can and it works similar to other non-mitel headsets. You turn the headset mode on and use the speaker button to answer and Hangup. You should also be able to use the button on the headset itself to answer calls too. Normally this is the case when using the Mitel Headset with the Attendant Console software so you can answer via clicking on the call or the answer button and it comes through the headset.
Thanks,
TE