After ICH.

[jbadge]

After 2 weeks of Copper treatment. How do I intro. my fish to the main tank again?

 

[elfdoctors]

The main tank should be fishless for a full month to allow the ich that was in that tank to have completely died off.
Most people would remove the copper in your QT and watch the fish for several weeks anyway to make sure that your infection was eradicated.