Ditto, the scented item is really good idea!! Like a pillow or a blanket with the smell of the new dog on the bed of the existing one.
You can also let the new dog smell around the house without the presence of the existing dog. Then crate the new dog in an obvious place and let the existing dog "discover" the new member on it's own and heavily reward with treats, hugs etc. (be careful to reward only good behavior). Then slowly let them sniff and play with each other! I wish everything goes well!! Congrats on the new addition!!
I think supervision is the key, especially during the first month!