When using the Telephony feature, Yesware will simultaneously generate a dialer box and a 'call details' box. You must use the 'call details' box to log the call task into Salesforce and write any notes on the call.
If you only see the RC dialer pop, check to see if the 'call details' box is behind the chrome screen. Hover your mouse above the 'chrome' icon, and you should see the 'call details' box. Click on it to bring it up to the forefront.