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First step, like any other trade, is to go visit your trainer and pay him 10- this will let you skill up to 75.
After that you can go to any trade or cooking supplier and buy the Simple Flour and Mild Spices you need.
From here on out, cooking is very easy. Just collect the raw ingredients needed and buy the recipes listed on these pages and you'll be at 375 in no time. The shopping list will give you an overview over which monsters to kill for the different ingredients.
Upon reaching 75, you will have to go see your trainer again and pay him 5 to be able to continue skilling up to 150.