In case you have a few email accounts added in Outlook, by default you can send as first added account. I will show you how to in simply way configure additional addressess to be able to send as. By default field FROM is hidden and we need to make it visible. In order to do that lets open New message window and then click like on the picture.
Next step will be adding our additional email address. In this way click FROM field and click Other email address.
In next windows put email address and click OK.
After confirm, you will be able to choose another address to send it as.
If you would dont need it more, just click X next to the email to remove it.
