Find a recipe that serves four. Then increase each ingredient in order to turn it into a recipe for six. This means you'll need to multiply each ingredient by one-and-a-half.
There are several ways to do this, depending on the original value you're increasing. For instance, if the original amount is 3 tablespoons, it's probably easier to just multiply 3 times 1.5. But if the recipe calls for 2 teaspoons, it might be easier to just use one (2 teaspoons) and a half (1 teaspoon) and then add them together to get 3 teaspoons. Find a method that works best for you and your recipe.
Now enjoy what you've made. Next time, make it a little harder by increasing the recipe so it serves 5 people.