A good starting point for a loose-leaf herbal infusion is about 1-2 teaspoons (roughly 2-3 g) of the blend per 200-250 ml of water. Use water that has just been brought to the boil, around 90-100°C, and pour it directly over the leaves. Let it steep for 5-10 minutes, then taste and adjust. Because the leaves are fermented, flavour releases more readily than with plain dried herbs: a shorter steep gives a lighter, milder cup, while a longer steep brings out the thyme and the deeper, smoother notes of the fireweed.
There is no single correct way to brew this tea. You can make it directly in a cup using a strainer or infuser, or brew a whole pot and pour it through a strainer. If you find the drink too strong, use slightly less leaf or shorten the steeping time; if it tastes thin, add a little more blend next time. Water temperature does not need to be precise, as long as it is near boiling.
After the first brew, the used leaves can sometimes be infused again with fresh hot water, but the second brew is noticeably milder. Whether that is worth doing is purely a matter of taste. Keep the unused tea in a closed container, away from moisture, so it stays fresh for the next cup.