Yes, this is fine to do although we must gain permission from the additional person. Please email firstname.lastname@example.org and copy in the person you wish to add. The person just needs to respond confirming they are happy to be named on the account and we shall do the rest.
Have a question we've not answered?
Let us know and we'll do our best to help. Furthermore, if it's a question that comes up again we'll add it as an FAQ to help others.