Adobe Portfolie, how to set a picture up so it look sharp.

I`m making a homepage in Adobe`s Portfolie.

Do you how to set op the pictures so the look sharp on a retrna monitor?

When i set my pictures up in 522px x 652px and 72 pixels/ inch, they look sharp on my EIZO monitor, but

unsharp on a Mac retina monitor.

What can i do?

B.