Tradesports is an exchange - like the New York or London stock exchanges for example. When you buy shares you are buying them from another member of the Tradesports exchange. And when you sell shares, another member of the exchange is buying them from you. You do not buy shares from Tradesports, and Tradesports does not buy shares from you. You are always trading shares with other members of the exchange - other people who are buying and selling shares, just like you.
It is important to remember that Tradesports is an open market. This means you may not always be able to get what you want. If you are looking to buy some shares, but nobody is selling, then you can't buy the shares you want.