In order to record calls made by the dialer from a campaign you must enable the Record All option in the campaign settings. To do this you would click on the Campaigns Tab as show below.
Next select the Yellow Pencil to the right of your campaign name to Edit Settings
Next check the box for Record All option at the botton and click Save Campaign
To listen to the campaign recordings you would click on the recording link to the right of the campaign in the Campaings Tab as shown below. You can view the recordings in a web page or by downloading a csv file with the recording links, all recording are saved for a period of 30 days.