Measure out 18 g of coffee beans. You’ll be pulling 36 g of liquid out. If you’re using Espresso Series 1, you can use the preset espresso profiles and it will tell you how much coffee to use, typically 18 g.
Espresso grind settings can vary wildly grinder to grinder. Opus Conical Burr Grinder has a suggested range on the inside lid, and we recommend starting somewhere in the middle of that range. Always remember to grind finer to slow down your shot, and coarser to speed it up.