ONSCREEN If your image appears in low resolution onscreen, right click (CTRL-click on Mac) on the image and go to Display Performance>High Quality Display. This will present the image in high resolution. To show all images in high resolution, go to the View menu and choose High Quality Display.
IN PRINT If your image appears in low resolution in print, check your print settings! In the print dialog, make sure you are printing with Graphics:Images:Send Data:ALL Do not choose optimized subsampling.
Why does InDesign default to display low resolution images? - - SPEED - - Enabling high resolution slows your computer.