Try to make sure that they are near the same age. Also, starting with the same sex is normally recommended when they are young, however since you didn’t do that, we have to work with what we’ve got.

The best way to introduce them is as follows.. You are probably going to need another cage but it shoudl work out for you..

Set the cages side by side, but not close enough that they can reach each other. On a nightly basis, swap their sleeping pouches or nest boxes so they become familiar with each other’s scent.

You are likely to observe that they will begin to “talk” to each other. Every day or two, try introducing them outside of the cage until they “connect”.
It isn’t recommended to introduce them inside one cage or the other, because they need to not be overcome by the scent of the glider that owns that cage.

Once they realize that this could be the beginning of a lovely relationship, you may want to put them in a neutral cage to let them start off on brand new turf together.

You can create the neutral cage by sterilizing the cage you intend to use and its contents so the predominant scent of no one glider is established.

Older male sugar gliders are the most likely to show aggression and territory defense activities. If he is an alpha male, he may never accept another male as a suitable companion.

However, if you bring in a female, it is very important that the female be at the age of maturity before you introduce them
The male will try and breed the female whether she is ready or not. This could cause severe injury or worse to the female.

You will find some great advice on sugar gliders here
http://www.sugar-gliders.com/glidervet-5.htm#intro
Good luck, don’t give up and I’d say.. get that second cage and keep trying.. They are territorial but they are so much happier when they have company.