Well it depends on if you have a PC or a Mac. If you have a PC, you can download LDD, then save a model with the parts you want and open the resulting .lfx file in studio. I haven’t figured out how to add decals to complex surfaces yet, but in theory you could import the model from studio into part designer and do it there. Otherwise you can simply add the decals in a photo editor post-render.
If you have a Mac, unfortunately LDD is no longer supported. What you can try to do is look up a lego set that has the part you need and see if someone else has made an LDD model of it already. Example: https://www.eurobricks.com/forum/index.php?/forums/topic/49784-kieldaman’s-star-wars-creations-in-ldd/ (the hyperlink wasn’t working for some reason) From there, the process is the same - open up the .lfx in studio.
Hope that helps some!