After you have created a listing to give away or sell, it will appear in the marketplace. Interested parties can reach you directly via private message through the green "Contact Seller" button. Your own listings do not show this option; instead, you can edit your post.
After you have created your listing to give away or sell, it will be displayed in the marketplace. Interested parties can contact you by clicking the "Contact Seller" button.

With the green "Contact Seller" button in the listings, interested parties can easily send you a personal message.
Since the system does not allow you to send private messages to yourself, you will not see this option on your own listings. Instead, you will see functions to edit your post.
Potential buyers see this green "Contact Seller" button on your listings and can use it to send you a private message directly.