You can start to add the products under each category here. Just select the leaf level category first, then, enter the fields in the bottom section of the screen and select 'Add Product'. Note, you can add products only to the leaf level categories. 

To edit a product- select the category->'Product Name'->then in the following screen you can edit the details. When you are finished, select 'Save Changes'.

To delete a product- select 'Delete'. Keep in mind, please make sure that you are deleting the correct product because this action is irreversible. 
  