If you would like to add new products to a marketplace, you need to have certain information to get the product online. The needed information can differ per marketplace.
For example: if at the marketplace bol.com a product is already known (maybe because another seller offers it), you basically only need the EAN code, a stock, price, and delivery time to put the product up for sale. If bol.com doesn't know the product yet, you need to create a product mapping for the product(s). With product mapping, you deliver necessary product information to the marketplace to create the product.
To read more about product mapping, read this article.
In general, the best you can do to make sure you delivered all the information you needed to get the product online, is to contact the marketplace and ask what they exactly need to put new products online. In most situations, a product mapping and basic offer information (EAN, SKU, stock, delivery time, and price) will be enough.
Finally, a little tip: check out the page that contains all the information about the specific marketplace. Sometimes there are channel-dependent details that you can check. The link to the information can be found here.