It is not uncommon for people to bring home a second dog, and often do not know how to help facilitate a positive introduction. This video does an excellent of of demonstrating how to do that in a neutral place. It also talks about acclimating a newly adopted pet upon your first arrival home.

Parents, YOU Are ALWAYS Teaching
Teaching happens whether we intend it or not. Our interactions cause others to learn positive AND negative associations with situations, and with us.