When introducing a new ferret, all ferrets will not get along, but if both ferrets are young, you have will have a much better shot at it. Introduce them on neutral territory (where they usually play). I let them sniff each other’s butt before putting them down because if they won’t let the other one sniff, they definitely will not get along. I hold one above the other and let them sniff for a few seconds and reverse. Then I put them down facing each other. Most young ferrets will just sniff and maybe dook a bit. Jumping on each other and biting the scruff is normal to play as long as they aren’t viciously shaking the other one, and you don’t have “flying poop”. Flying poop is when they attach to each other, chitter and screech, roll, and one or both poops while rolling (flinging poop everywhere). Sometimes if they get too rough, you can pick them up, calm them down and let them try again. The WORST possible thing to do is have them side by side in a cage where they can see each other, or across a gate. That brings out territory issues. Put them on the floor and see if they can work it out.
Like I said, jumping on each other and biting the scruff, even dragging across the floor, is normal. They have to establish which one is the boss. Usually, there is a little bickering from time to time, and you’ll find them sleeping together later. When people adopt ferrets, I tell them to let them sleep separately but play together, and when you find them sleeping together you can put them in the same cage.
You will need to have regular playdates for your female to continue to accept the male. Often females hit 3 or 4 years old and decide they don’t want any new ferrets in their life. Not all are like that, but a significant number do behave that way. So you need to let them play regularly enough that she still accepts him. You might even have a “sleepover” once a week to reinforce it.
Again, the worst thing is to let them see each other (except for those few seconds when you let them sniff butts) without touching. The best way is to let them dook it out, giving them a rest if one gets overly agitated (poofy tail, running like crazy or getting really rough). A little poofy tail when the meeting is normal. The way to tell if they are playing or fighting is if one jumps the other (and they roll around with no flying poop) and the jumper gets up and jumps on the other ferret (and doesn’t just run away). If the play is relatively even. If one ferret constantly hides and shakes a lot while the other pursues, they might not get along.
Some screeching (if one is inside a tube, the other comes to look and the first one screeches) is normal. The screeching one is scared. Sometimes they will get used to each other (especially if the other one does not jump the screeching one), sometimes they won’t.