Click on the menu icon in the top left > all tools > Catalogs
Click on Create Catalog
Select E-commerce as the catalog type and click on next
Select Upload Product Info choose who ownes the catalogue and enter a name.
Select the business type (if available) and enter a catalog name, click Create and then Create
From the left hand menu select products, then click on add products.
Now click on Use Data Feeds
You can now start creating a product advertising catalogue.