Containerized citrus trees can be planted throughout the year because you are transferring the tree and there is minimal shock involved. When replanting you will want to select a well draining soil as citrus trees do not like to have drowning roots for an extended amount of time. Wet roots can create issues of disease and leaf yellowing. Furthermore, container citrus trees can benefit from adding rocks or styrofoam peanuts in the bottom of the pot so that there is room for the water to retain to, and eventually leave the pot so that the roots stay dry. Always select a pot with holes and a caster that sits underneath the pot.
Pick a spot with 50% or more sun on well drained soil or soil mix. Preferably where it will have protection in winter from cold north and west winds. Avoid septic tanks and drain lines. Clear away any weeds and grass because you don't want competition for the fertilizer and nutrients that you may apply.
Have water available and dig a hole larger than the container the citrus tree is in. Remove your tree from the container and shave away fiber roots from the side of the root ball (Important). You are most concerned with the roots that are growing in a circular direction around the edge of the root ball where the pot was. By loosening and trimming these roots you are allowing for roots to grow out into the new soil environment that you are placing the tree.
Place your citrus tree in the hole that you have keeping the top of the root ball at the same level as the existing ground level, no deeper (Important). Planting trees to low in the new hole will cause issues where the tree may not survive. Once the tree is placed in the hole and the crown of the root ball is at ground level go ahead and fill the hole 1/2 full with water. This will remove any air pockets and help the tree settle in where in wants to be.
Finally, fill the rest of the hole with the remaining soil to ground level, pack soil to remove air pockets. You can water again if you wish. This will help in removing any other air pockets that may have happened when finishing the soil fill in.