After you selected your panorama type to be partial - the next thing to do is - orientation. First of all, let us suppose the panorama in question is this one:
...and let's suppose, the position on the map is:
First of all, unlike the "full" cylindrical panorama - partial panoramas cover only part of the field of view around the location. For example, the field of view of our panorama is...
Now, the proccess of orientation consists of finding the directions of the left and right directions on the panorama:
On the map:
So, now you should click twice on the map. First click anywhere on the line marked "left", and second click anywhere on the line "right". The order (first left) is important! After the second click on the map you should be automatically redirected to the finished panorama. Note that the left and right lines are not visible - you must imagine them on the map.
And, of course, if the resulting panorama orientation is not correct - just click "Edit" (on the page with your panorama, below the map) skip the first two steps and try your orientation again.