Step 1: Open Outlook 2010.
Step 2: Click the New E-mail button at the top-left corner of the window, as though you were going to send an email. You do not actually need to send a message to do this – the option is just located on this window.
Step 3: Click the Options tab at the top of the window.
Step 4: Click the From button in the Show Fields section of the window. You will notice that the BCC button is right next to it. This is also where you go to display the BCC field on messages.
You will now see a From drop-down menu above the To field, from which you can choose the email address that you want to use to send the current message. The From field will remain visible until you choose to disable it at some point in the future.