Make sure you have a second cage and make SURE you do a 30 day quarantine, just in case. Some issues take a while to show up, and you don't want your own chin at risk.
Quarantine means separate cage in a separate room. Platyimes in different rooms, no sharing of toys, washing hands between contact. You'll be glad you took these precautions if something does come up, and if not, at least you took the safer route.
After quarantine is over, bring the second cage into the same room with your own chin. Park it across the room, and leave it there for at least a week. Continue to take the new chin into a separate room for playtime. This gives your chin time to adjust to the scent of a new animal in the room with them.
After a week, move the second cage closer to your chin's cage. Leave at least 6-10 inches in between them to prevent any injuries through the bars. This will give them the opportunity to "talk" and get used to the idea of having a neighbor.
If all goes well, wait another week or so (at least) before you try introducing them to each other. Playtime is the best time for intros.
When it's time for introducing them, it goes easiest if you pick neutral territory, like a room not usually used by your first chin. I use the bathroom. I bring them both into the bathroom in separate carriers, and let the new chin out first and then my first chin. Some initial chasing and/or fur slipping is normal. You just want to watch for biting, or serious fighting. Be prepared to separate them immediately if it goes bad. I think a distraction is helpful, so I dry out the tub thoroughly and put a LOT of dust into it, so that both can roll comfortably. The dust also helps "neutralize" each chin's scent and that makes it go smoother.
I do these neutral territory playtime for a week or so before allowing them to play together in my first chin's regular play area. That also helps get them familiar with each other before your chin has to "share" her regular space and toys. If the neutral territory playtimes AND the shared area playtimes go well, then you can think about letting them share a cage.
It's best to pick whichever cage is largest. Also, if one chin seems more dominant than the other, pick the cage of the less dominant chin. It helps to even the dynamics out so that one doesn't feel as bossy over the other.
Scrub the cage down completely first and then move items from both cages into the cage you choose. You want a nice even mix of "property" in there to keep the scents balanced. Watch them closely for a couple of weeks.
With females, you are probably going to have to deal mostly with kacking and spraying moreso than actual fighting or biting. (usually)
Good luck!