Вот подробная инструкция:
To change the spine of a blended object
The spine is the path along which the steps in a blended object are aligned. By default, the spine forms a straight line.
To adjust the shape of the spine, drag the anchor points and path segments on the spine with the Direct Selection tool.
To replace the spine with a different path, draw an object to use as the new spine. Select the spine object and the blended object, and choose Object > Blend > Replace Spine.
To reverse the order of a blend on its spine, select the blended object and choose Object > Blend > Reverse Spine.