Arum Lily

Silver Surfer

Hello, On the 9th June I bought an Arum Lily on line from a well known Company; it arrived 2 days later well packaged and looking healthy, not in bloom but it had some green leaves. I looked on line again and they said it could be put it into aquatic compost and be kept in water. I did this but now it is not looking very healthy and the leaves are turning yellow and dying off. I got back in touch with them, sent them a photo as requested, and they suggested putting the Lily back into compost, as they thought the water was too warm, (which it wasn't). I've now put it back into fresh compost and it does still have some of the original compost around the roots. Can anyone suggested where I should put the pot now to, hopefully, recover and should I keep it very wet and in the shade?