While testing the application I have come to conclusion that there is no feature regarding calls recording and on the support form there are questions related to this matter. On the other hand, an official person responded that this features was noted for the future releases.
Also, since Tango is a desktop application, you can use a desktop recording software which captures both image and audio content. For this job I simply recommend Camtasia Studio because it is easy to use and has editing capabilities available.
Download and install the software using the package provided and follow the on-screen instructions. Upon starting the software, a tutorial will greet you teaching on how to record your screen. You can then later export your content to various file formats.