Continue writing the next sentence.

How to introduce a new dog to your senior dog
Keep your senior dog visually separate from your new dog.
Place their cages at opposite ends of the house and keep them entirely separate for the first few days. During this period, you should take measures to make sure your senior dog does not see the new dog.
For example, you should not let them both out of the house at the same time and should keep them in different parts of the house. Introduce your senior dog to the new dog via scent.