Fernando, Just add the camera image that contains the two image circles. PTGui will create a duplicate image and crop/mask the right and left sides so that image 1 has the left side active and image 2 has the right side active. Your resized sample image doesn't have exif data containing the camera data, so that won't work, but your original camera images should be ok. There is very little image overlap so you may need to help things along by adding some control points manually. Even so, lens parameters can't be evaluated accurately without an adequate spread of points. If you have not already done so, you can calibrate the lens parameters by shooting two panoramas, pannng the camera through 90 degrees. You then stitch (align) them together in PTGui with a wide spread of points.
John