Your new tree
Bare root trees and plants can be planted any time during the dormant season usually from mid November to mid March. You should plant bare root trees and plants in their permanent position as soon as you can after receiving them. While it is always best to plant the trees as soon as you can, it is sometimes better if conditions are not right to wait longer and plant when conditions improve. In any event you should always plant before spring growth and not plant if the ground is frozen or waterlogged. Frost is usually not a problem once trees have been planted. The above ground parts are hardy. The roots can be damaged by frost but frost in this country rarely penetrates far beyond the surface inch or two. However it is always a good idea to mulch the area around the tree after planting as this insulates the surface and prevents the risk of frost from penetrating and damaging roots. Straw, garden compost or leaf mould make excellent mulching. Spread some around the base of the tree and cover with a thin layer of soil to stop it from getting blown away. Waterlogging is often a more serious problem. If your soil is prone to waterlogging it is best to plant in late winter/early spring when the ground is starting to dry out.
If for any reason you are unable to plant immediately you can keep bare root trees and plants in one of the following ways depending on how long you need to keep them for. If it is a matter of a few days you can just leave the package in a cold but frost free place such as an unheated garage or shed. If it is for a longer period the best option is to heel-in the trees. To heel-in, dig a trench ideally in a well drained position with light friable soil. A shaded position is best as trees would maintain dormancy for longer and would also be better protected from ground frost. Place the roots of the trees into the trench keeping the trees tied up as a bundle as packed. Cover the roots well with soil. Cut the ties holding the bundle together. Loosen and shake the roots to ensure the soil get all around the roots. If your soil is too wet or heavy you can use peat, compost or sand to cover the roots. Use straw or garden compost mulching to cover the soil as it will help to prevent frost from penetrating. If you have a rabbit problem you should ensure that the trees are protected while heeled in.