You can sign up as a seller, buyer, or both. If you are only interested in buying, you can skip the seller profile setup section. Similarly, if you only intend to sell, you can skip the buyer profile. If you are interested in both, you can complete and apply for both profiles.
Any firm can sign up as a seller but only firms using Karbon can sign up as a buyer. If you do not have a Karbon account, you can still be added on the marketplace with all the same functionality except you will not have a "Karbon Verified" designation.