If the weather is unsuitable for planting on receiving the hedging then dig a hole and bury the roots of the bunched plants. (storage prior to this should be inside away from possible frosts.) They can be stored like this until planting becomes possible.
When planting you either plant them in a single row 4 per metre. Or a double staggered row 6 per metre. The easiest way is to dig a trench down to the required depth. They need to be planted to the same depth as you can see above the roots on the whips. Place the whips in the ground spreading the roots out carefully. Then backfill so they are secure in the ground. Water the ground then leave.
After planting it is advantageous to mulch the hedge with lawn mowings or leafmould to suppress weeds. If preferred this can be done using plastic or carpet ground cover placed around the plants and covered with soil.