Thank you very much Old Toad and Todd Dixon - it worked. And I am extremely grateful to you both.
Dragging the "iPhoto" in the package to the "user" part of the dock also works like a charm. But I earnestly hope Apple will reinstate a straight-forwardly functional iPhoto without the need for work-arounds.
And it is about time that Apple realised that taking away things that work and that have had a LOT of time invested in them by their users is not acceptable behaviour; we've seen it with the iWork apps as well, and once upon a time LogicPro. Also they should realise that many households have a multiplicity of equipment at varying levels of up-to-dateness - in our case, on top of this MBP Retina with Yosemite, we still have a Snow-Leopard machine (White MacBook, Core duo) and a Mountain Lion machine on which it would be folly to install Yosemite. And all photos on external discs, with a different level and version of iPhoto on each computer used to access the same basic collection of photos.
Also, with nearly 50 GB of iPhoto library and over 200 GB of photos, an iCloud solution would be expensive and slow, even with a high-speed fibre internet connection.