Navigate to the settings of an existing ticket or product or create a new ticket or product. Go the the restrictions tab and set an inventation code. This ticket or product is now protected with a code so that it will be hidden in the checkout. Only people who you share the code with will be able to access and purchase it by entering the code.
A link is generated with the inventation code included. Copy the link and share it with the people who may see and buy this ticket or product. With this link the inventation code will already be selected in the checkout and the ticket or product will be visible.