welcome to YT!
not sure how to do the introductions "properly" but when i introduced mine, i would keep the x-pen between them for a little bit and let them sniff one another through that...once they seemed "okay" with one another, i would put them together and sit on the floor with them to see how they interacted...i guess i got lucky because each of mine became friends really quick
good luck and congrats on the new baby!