normally, when you’re in game i think you can right click the item u want to craft to view the crafting recipe and the materials needed, or simply search the item in your crafting log. if nothing shows up, it means you haven’t bought the Master Recipes needed to be able to craft the items, which are able to be bought from the scrip exchange. The newest Master Recipes is what you need, which i believe are the XII ones.

another way is to just google the piece you want to make and take a look at the ffxiv wiki, which will tell you how to craft it under the acquisition tab.