How to Make a Tea Cup and Teapot in Simply Tea
Fire the ceramics first
You cannot brew anything until you have a Tea Cup and a Teapot. Both start as unfired items: craft an Unfired Tea Cup and an Unfired Teapot, then fire them. The mod registers two ceramics:kiln recipes for these, so a kiln is the intended processing block. If you do not have a kiln yet, the smelting recipe type is also present in the mod, so try a furnace as a fallback.
Once fired, you have a Tea Cup and a Teapot ready for brewing.
Brewing setup
With a Teapot in hand you can produce the filled cups. The mod's recipe types include crafting_shapeless, crafting_shaped, campfire_cooking, and smoking, so tea production is not limited to a single station. Check your recipe book (or JEI/REI if installed) while holding the Teapot to see which inputs it accepts.
Tea bags are the other half of the chain. Craft a Tea Bag, then the flavoured variants: Black Tea Bag, Green Tea Bag, Dandelion Tea Bag, and Chorus Tea Bag. Each bag corresponds to a cup: Cup of Black Tea, Cup of Green Tea, Cup of Dandelion Tea, Cup of Chorus Tea, plus Cup of Chai Tea, Cup of Apple Iced Tea, and Cup of Hot Chocolate.
Keep at least one spare Tea Cup and Teapot — ceramics break the flow if you have to refire mid-session.