What is the most logical next event?

How to introduce a new pet rat to another rat
When you bring your new rat home, don't have it in the same room as your other rat until you're sure it won't pass on any diseases.
Wash your hands between handling your rats. Some people choose to quarantine new rats from the others for several weeks.
When you're ready, place the new rat's cage in the same room as your other rat's cage, but about three feet away. This should get them curious about each other and used to seeing and smelling each other.