It's important to have good soil preparation. You'll need to create a hole large enough to hold the root ball of the plant. Start by making the hole one-and-a-half times the size of the root ball in the shape of a wok with slanted sides, meaning once the plant is in the ground it will have some loose soil around the root ball for it to be able to begin establishing its roots.
Carefully remove the plant from its pot or bag. To assist your mature plant in establishing a solid root system, it's often recommended to delicately loosen some of the soil around the existing root ball. Avoid sun exposure to the plant's root system as much as possible to prevent any root damage. On sunny days, put your body between the plant and sun so your shadow covers it, but it's best to plant on cool, overcast days.
Carefully place your tree into the pre-dug hole and begin back filling the soil around the plant. Ensure you do not plant your tree any deeper than it was sitting in its pot, and keep the root ball even with the top of your soil. Be careful not to pile extra soil around its trunk.
Once you've planted, it's extremely important that you thoroughly water your tree to settle the soil around its roots. Insufficient water after transplanting is one of the greatest causes of transplant shock. Most plants can't take in water through their leaves for the next few days, which makes a well-watered soil even more important. It'll also take a while for the tree to get its roots out into the surrounding soil and establish itself. So, your plant will need consistent watering during this period, especially in warmer weather.
Mulch and stake your new plant to help protect it from the elements. Mulching has many advantages including helping to maintain moisture in the soil, assisting in weed prevention, and helping to regulate soil temperatures. This will assist in limiting the stress on your newly planted tree. Staking of new trees will help stabilise your tree and protect it from any strong wind damage.