I don’t know what more you want from me. If his actual contributions (some of which are listed on this very thread) aren’t sufficient, maybe you want a quote from Darwin using the word “eugenics” and explaining in detail how to practice it. You might as well ask for a detailed wiring diagram of a modern car, drawn up by none other than Ben Franklin.
Darwin’s contributions to eugenics are not in any way comparable to Jesus Christ’s contribution to the salvation of mankind.
Of course there is a connection between Darwin, Darwinism and eugenics. Here is an offhand list of great Darwinians who were eugenists:
Leonard Darwin, Eugenic Society, president
Charles Galton Darwin, Eugenics Society, president
Julian Huxley, Eugenics Society, president
Francis Galton, Eugenics Society, founder
R.A. Fisher, Eugenics Education Society, etc.
Karl Pearson, Galton Professor of Eugenics etc.
R. Lewontin, American Eugenics Society, president
J.H. Kellogg, American Eugenics Society
H.H. Newman (of scopes trial fame)
H.F. Osborn, American Eugenics Society
Ernst Rudin, infamous
H. Davenport and Harry Laughlin, infamous
And many, many others.