The Skill
You can acquire this skill by choosing a recipe from the 'Preserving' menu in the Brazen Homestead Cookbook & Craftbook.
This is a 10-level skill. As your sim levels up this skill, various interactions become available. Social options allow sims to chat about or give tips on Preserving. Additionally, there is a club activity for Preserving, which requires the Get Together pack.
Preserved Goods
Most recipes will yield 8 servings that can be measured from a bulk item, like a grain sheaf or basket of herbs. Some of these ingredients can be eaten once they've been properly preserved.
Ingredients
Unless you have the 'Simple Living' lot trait active, all ingredients are optional. If you use ingredients it will reduce the cost of the recipe. There is also a 'Bacto Cultures' ingredient included with this that can be collected from spoiled meat if your sim has level 9 in this skill or is a Botanist.
Skill Max
As your sim levels up, additional recipes will become available based on the custom recipes you have installed. Once your sim reaches the maximum level in this skill, they can sell their bulk preserved goods to the local Food Co-Op at a higher price.