New product pages that you create need 2 things to appear 1) they need to be assigned to a manufacturer and 2) they need to be assigned to a category
1) If you want to build product pages for an existing category, simply build the page, in the right sidebar of the page editor, enter the manufacturer name in the manufacturer field.
Then select the category you want to assign this product to and publish the page. Once the page is published, the product will automatically be added to the product menu.
2) If you want to build a new category to add products to, simply select Category on the left sidebar in the Product area. Here you will enter a category name, upload an image and assign the category to a parent category (if necessary),
Then do Step 1 by building product pages and assigning it to the category.