Personally I'd siphon, mix, then at the end of the de-gas sprinkle in the K-meta.
From that point on Follow the instructions. As to aging, that's again a personal choice to make. What variety of wine is this kit? That can make some difference.
Be patient, there are a lot of experienced kit wine makers on here who will have much more experience to share with you.
The one consensus is that the kits 9 out of 10 times have you bottling too soon.
Biggest lesson, toughest lesson to learn is patience.
I'd love to bottle my peach wine started this past Summer but it still needs at least 2-3 more months before it should be bottled.