It is impossible to sell a product on Sales Jet without a funnel. You will need to create a funnel and add a web page (site) to it. For details on how to create a funnel see the article "Creating a funnel".
For a descriptoin of how to create a webpage see the article "Creating a new page".
When you have created a web page, you will need to populate it in the Page Editor to add elements that allow visitors to buy your product (Elements are things such as buttons, menus, text fields). In addition to any other content you put on your web page, you must have a purchase button allowing the visitor to add items to cart and then proceed to checkout. Read more about these elements and how to set up your web pagein the articles "Page Editor", "Button Element" and "Icon Element".
If you choose the action Purchase, then when someone clicks on the Purchase button will will automatically be redirected to the payment page for the product / service selected. If you choose the action Add to cart then the visitor remains on the page, but a small window opens on the right showing the cart with the product added to it. They can then complete their purchase on the main page. The first option is used when you sell only one product per page. The second option is used when you have several products for purchase on one web page.
In order to collect payments you will need to connect payment methods. For instructions on how to do this, read the article "Sales Jet Payment Instruments".
If you already have a web page on Sales Jet you can create a link to purchase a product. You can send this link to your customers for easy ordering and payment. The point is that you do not need to make complex sites and funnels to sell product. You can sell product live and give those who wish to purchase a link to pay through Sales Jet. This makes it easy to sell products and services without having to physically handle cash and in-person payments.
You can also create pages and build funnels that will interact with potential buyers and sell your products and services through your Sales Jet web pages. For more details on how to build a funnel read "Sales Jet Flow".