On that page you would be able to add new product/service with fill up regarding information form fields.
Setup > Products and Services
If you want to set custom variation/fields for a product/service, then you will see a
+ button, with clicking that button you would able to set your desire custom fields.
The last 2 checkboxes are important and these defines - product/service status & would show that product on product listing page or not.
In category page - you would able to create new category, edit/remove existing category.
Setup > Prod/Service Categories