Where to Find Recipes for Your Workshop

There are two types of recipes available in your Workshop: Ship Upgrade Recipes and Fusion Recipes.

To unlock Ship Upgrade Recipes, you need to research them in the "Hull Upgrades" tab of the Ship Lab.
Once researched, they will automatically appear in the Crafting Tab of your Workshop for use.

Fusion Recipes are more complex, and how you obtain them varies based on the type:

Core to Core Recipes:
These recipes allow you to fuse multiple lower-tier cores into one higher-tier core. To unlock them, you must first find at least one of the higher-tier cores you want to craft. Once unlocked, the recipe will remain in the Fusion Tab of your Workshop permanently.
Pattern to Core Recipes:
This type of recipe allows you to break down a higher-tier ship pattern into a lower-tier core. The recipe appears in the Fusion Tab once you find a pattern that can be broken down. However, if you use up all of that specific pattern, the recipe will disappear. It will reappear once you collect more of that pattern.