How do I print a DVD Cover design as an A3 showing the crop marks? (On Indesign)

See if your printer can supply you with a template for the DVD cover, or a similar printed copy, so you can copy the dimensions.

If not, create an InDesign document with Print as the intent select, depending on the size of your design, A4 or A3 landscape.

Create your DVD design in the middle of the A4/A3 space, Place any Photoshop images in the InDesign doc (make sure the images are in RGB color mode) and in the InDesign document add the text, coloured backgounds etc and allow for Bleed and (if you haven’t been given a spec by your printer) select the InDesign PDF preset, PDF/X-4 and in the subsequent PDF dialogue box, tick crop marks and Use Document Bleed Settings and single page