As it is pot grown, you can easily leave the plant in its pot for a few days/weeks before planting it. Just ensure you keep it well-watered and it gets enough sun. Don't leave the plant for too long, however, as you don't want the roots becoming root bound.
As Hypericum 'Golden Beacon' grows a large crop of flowers in one Summer, you will need to prune the plant every Spring. We also highly recommend carrying out a renewal prune (where you cut back about 1/2 of the plant), every 3-4 years. This will encourage the plant to produce new, healthy foliage.̴Ì?