Paying with DOT
If you selected payment in DOT, you should see a screen like the one below.
From here, click on Connect to polkadot{.js} to connect to your DOT wallet in your browser.
Once the wallet is connected, you should be able to see a dropdown list of wallets. Select the wallet address that is the one which has your DOT funds. This is the wallet address you'll be using to make payment.
Once you select the right wallet address, just click Submit Transaction.
At this point, you will see a message: Waiting for Confirmation. At this point, you just need to wait for Tokensoft to verify that your order is submitted on chain. Once that's done, you'll see a Thank You screen with a green check mark. This means your transaction was successful.