When you are in Home view: Choose New Mail or message you want to reply and click reply/reply all/forward.

 

Select Options and enable Show From

 

After this you can click From -button and select Other email address. Put your cursor on the right side of the From -button and click to activate the field.

 

Enter the address you want to use that is available for you (you can check the available addresses from OMA service and you can also use group email address if you have rights to one) and select Use this address