InDesign 'places' an image into a document - using the commands: File/Place.
Image Size is important, as InDesign needs large images to scale down rather than an exact size image to place, to ensure the image is sharp.
You can always make a large image smaller, but the reverse a small image cannot be made larger, as it pixelates!
Images need to be at least 1000px wide (for a horizontal image) or 1000px high for a portrait image.
Then using the corner of the image and the shift key, you resize the image to fit into the document. On some keyboards you need to use the CTRL key and not the shift key. Try the options first to ensure you have a constrained proportions image.
Sometime even a large image could look pixelated in InDesign, which can be misleading. The cross-check here is to save the file as a .pdf and view the 'final product'.
An image that is small just won't work at all!