Answers

Can I use a product photo from the store website?

Yes, and it is the normal way to do it. Paste the product link and the photo and the dimensions are taken from the page together. If the link does not work, save the picture and upload it.

Which photo you pick matters more than people expect. A plain shot of the item alone on a white background works best, because everything in it belongs to the product.

Avoid styled room scenes. A sofa photographed in a furnished set carries a lamp, a plant and a rug, and those get read as part of the product. If the shop only has room scenes, crop the image down to the item.

Several angles help for anything with structure — a shelving unit, a bed with a headboard, a chair with visible legs. Two or three pictures of the same product give the model a chance to keep the details that a single front view hides.

Ignore the size written on the picture. Marketing overlays and dimension arrows drawn on the photo are read as part of the scene and can end up rendered into the result.