If you're the manager for the pool, a "Manage Pool" button will appear near the top of the page. Click the button to go to the Manage Pool page:
On the Manage Pool page, click the "Select a token" button in the "Swap" section. A modal will pop up, prompting you to choose a token from the Tradegen token list:
Choose the token you want from the menu, then enter the number of tokens you'd like to swap in the "from" field. If you want to switch the order of the swap, click the arrow in the center of the "Swap" section.
Click the "Approve" button to give the pool contract permission to swap tokens. Once the approval transaction completes, click the "Swap" button to finish swapping.