This is the alpha stage of the mod so if you find any bugs or if you have any suggestions please submit them on issue tracker.
Start by breaking grass blocks just like vanilla seed drop:
After you grow up your crops you can simply break them or you can cut them with tea scissors:
Once you harvest your tea crops you have to smelt them in a furnace and then put them in to kettle with cup and sugar(sugar is optional if you put sugar in a kettle it will give you speed effect if you didn't put them in the kettle you will have tea with no sugar and no speed effect after you make your tea in a kettle you can combine it with a sugar in a crafting table.)