The way you send the funds depends on what bank you intend to use. Your bank should have a feature or app to make the transfer possible.
You need to have a clearXchange account to tie your email address or phone number to your bank account.
To send the money you just need the email or phone# of your trading peer.
More info: https://www.clearxchange.com/faqs
To address the 2nd part of your question: Your trading peer has already locked the BTC into a 2-3 multisig address. If (s)he fails to confirm that (s)he received your payment, the funds will be release with your key + the arbitrator’s key and go to your account after you’ve proven that you’ve sent the money.