The way I see it you have a few options. I'm still trying to decide which would be best for my plan, but here's the two possibilities I'm wrestling with. The first option would be to make the tea, then use the tea as your boil/top off water. My second thought would be to add the tea at flame out after the wort has had a minute or so to cool, then steep for a few minutes before chilling the wort to pitching temps. I know people have also added to secondary, and/or left the tea in the wort during fermentation, but knowing how tea's flavor changes as it's left in hot water, I think you'd probably want to keep it as close to normal tea steeping as normal.