Welcome to the forum. What a pretty girl!
Read these articles on introductions.
http://www.sugarglider.com/gliderpedia/index.asp?Introductions
Before you start, you should quarantine the gliders from each other for thirty days. That means separate rooms, no pouch or toy swapping, and wash your hands after handling one. There will be a vet check for both at the beginning and end of the thirty days, including a fecal float and smear to check for parasites. One particularly nasty parasite, giardia, can stay dormant in an animal for some time; stress will cause it to manifest, and it can take as long as thirty days for the infestation to show in a fecal exam. It also will give your new glider time to adjust to his new environment and gain some self-confidence before meeting the older glider. They'll each know the other's in the house! You'll hear them barking and communicating.
At that first vet visit, it would be a good idea to have Gizmo neutered. Gliders will breed like rabbits, and unless you're prepared to deal with joey rejection (it happens more often than people think) it's best to not go there. If you do have joeys, he should be neutered as soon as possible after you know she's expecting, or you could end up with a second litter and more males to neuter, or the possibility of inbreeding.
After you've gotten that second all-clear from the vet, you can move the cages into the same room and start swapping pouches. Don't put the cages close enough for them to reach each other. Gliders are very territorial, and instinctively want to get rid of the "intruder"; they may fight through the cage bars.
Make sure that the gliders are both about the same size and weight before you let them meet. This could mean extending the separation period until Gizmo catches up to Sweetness. If he weighs, for example, 60 grams and she weighs 80, then he'll need a little more time. He's got to be able to defend himself if they fight.
When I introduced my boys, I did it in the bathtub. They fought like cats! I broke up the fights immediately and checked them, then put them away. This went on for about three weeks, every two or three nights. One night they were both on my knee and one took the other's paw very gently in his mouth; they stood still for about thirty seconds in that pose, and from that moment they were best friends. So don't get discouraged if it isn't all cupcakes and balloons at the beginning. Sometimes it is! I'll wish you that kind of introduction.