Ck whether lilies are hardy in your gardening zone. If YES, do nothing, let foliage die off on its own and wait for next year when they'll bloom again. If not hardy in your zone, they're annuals for you and you may remove if you need the planting space.

Asiatic lilies are very hardy - zone 4 , maybe even 3. I'd recommend planting them in the ground in a sunny location with well draining soil. They tend not to rebloom as proficiently if left in the container year after year. You can remove the top portion of the stems, where the old flowerheads were located, but otherwise leave all the rest of the stems and foliage in place to recharge the bulb for next year.

Lilies bloom just the one time each season so you will have to wait until next year for more flowers. And expect it to bloom later (June) once planted in the ground. Yours was forced into an early bloom for Easter sale.

I usually let them be for the summer...leave the leaves on them for them to build up energy with for next years return...but later in fall/early winter I'll dig up all the lilies and collect the little bulblets so that next spring i can get them started on their way to getting bigger. Once I've gotten the bulblets i put the original bulb right back in the same place it was.

since yours are in container I would plant them, or care for them just as you would if they hadnt bloomed yet...they should be able to bloom again next year. I had ones that got to be about 3' tall, even though they were in a container only only 4" deep. They bloomed for years like that and i never brought them inside or even changed the soil (tisk tisk on me for that!)

I'm actually not sure if they require a cold-snap in order to bloom next year...some plants do but i've never had anything that cant be left in the ground all winter so I dont know...but I'm sure someone else knows)