When your cuttings arrive please get them out of the shipping packaging as quickly as possible. The cuttings have a "top end" that is flat and a "bottom end" that is sloped. Each cutting will also have two sets of nodes. Each node is a pair of buds; the top node becomes stems and leaves, the bottom node (underground) becomes roots and shoots up stems.
Cuttings can be stuck directly into the soil but the ground is still frozen in most places when cuttings are shipped so you can start them inside.
When your cuttings arrive it is beneficial, but not necessary, to soak the bottom half of the cuttings for 12-24 hours in non-chlorinated water (well water, spring water, etc) Drain and allow to dry for a couple of minutes. Rooting hormones are not necessary and the only organic option that we have used is willow water but there are rooting hormones available in powder and liquid form. Our experience has shown that elderberries have such a high rate of success that rooting hormone isn't necessary. Place the cuttings, slope side down, about halfway down into a soil-less potting medium. We use nursery plugs but you can also use a pot (or whatever you have) and place multiple cuttings into it.
Water well and place the potted cuttings in a sunny location. Elderberries actually root best in a cooler environment and too warm of temperatures will promote only shoot/leaf growth. Keep watered at all times. Once danger of frost has passed place plant starts into prepared soil.
Elderberries do best with at least 6 hours of sunlight in well drained soil. For spacing keep in mind that they average about 10' tall and 6-8' wide. Once your plants are established they will send out suckers and fill in whatever area they are allowed to so keep this in mind when deciding on a location (maybe not near the property line!) In our production field we plant them about 2-3' apart in the row to minimize the open ground while they're getting established and we use mowing as the way of keeping them "contained" in their rows.
The first season it is very important to manage two things well: water and weeds. Make sure the plants get sufficient water the entire first season, and keep the weeds away to allow them to set down roots and reduce competition.
Elderberries are perennials and as such you can expect "sleep, creep, leap" which means the first year they look like the are sleeping but below ground they are actively setting down roots. The second season they are still establishing roots and have more growth above ground. The third season, and beyond, is when they take off. We recommend removal of flowers the first season in order to have the plant focus its energy on root production. You will be more than rewarded in subsequent seasons with strong, bountiful harvests.
In the upper midwest we cut the plants to the ground in late winter while still dormant. This practice provides the healthiest plants with the highest flower/fruit production. In our fields we feed the soil ecosystem with organic components because healthy soil means healthy plants means healthy people.