Most mail-order snowdrops are purchased as bare-rooted growing plants referred to as “in the green” and are usually supplied just as the flower is starting to fade and before the leaves have started to elongate.
When your plants arrive and they feel particularly desiccated with limp leaves then they will benefit from the bulb and roots being stood in water overnight and planted out the following day.
Any preparation for the planting site should have been completed beforehand to avoiding delay in replanting your plants.
On planting them in the garden the soil should be workable, not frozen. Plant the bulbs at the same depth that they have been grown at. Make the hole large enough so that the roots can be spread out. Place a small amount of sand at the bottom of the hole for the bulb to sit on. Firm in gently. Space the bulbs approx 3 to 4 inches apart to allow for clumping up. Water immediately and if possible, water daily for the first week, then every other day for the next week. After this period, the snowdrop should have recovered from the move and the foliage should now feel firm and will continue to grow. Keep the plants well watered during March and April if the weather is at all dry. Dead heading i.e. the removal of the seed pod is a personal choice. Let the bulbs die down naturally; on no account should the leaves be cut off or tied up.
If the plants fail to re-establish and go into premature dormancy, that is, the leaves wither away too early, then lift the bulb and put into a pot of moist sand and leave in a cool, dry place. Re-plant the bulb in the garden in August. It should hopefully grow next spring, but may not flower.