I think you're doing just fine too!
As Dottyy said, the other kitten intro topic in this section is quite good.
How long cats need to be apart can take anywhere from a day to more than a month, just depends on the cats. Just give introduction a chance when you are ready, there is no correct time really. But when you do introduce them, just do so one at a time. You might want to give them a week of letting one kitten out for a day, or half a day, and the other the next day, next half day. So they don't gang up on the resident cat, and it doesnt overwhelm her all at once.
Always supervise them, and keep them apart at night so everyone sleeps soundly.
When I've introduced cats in the past, I've only left them apart for one night and then got down to introduction business the next day, within a week everyone is settled. But not introduced two before.
Try letting one out for breakfast with your resident cat, just walk past them and to the kitchen, as if 'new kitty' isnt even there.
Cats are more compliant when they have fed, and also less grumpy.
Intro's must be calm and nonchalant affairs.
Keep a towel with you, to throw on them if they fight, but don't expect one, just relax!