Hydrangea plant

Most common hydrangeas are edge of woodland plants so are happiest in part shade.
Firstly water your plant, if you can put the whole pot in a bucket of water and leave for a good few hours, or even overnight.
Then dig your hole. Make sure that the hole is deep enough for the soil level to be the same when the plant is out of the pot. You can check roughly by putting the plant still in it's pot in your hole. Depending on your soil you might like to add a bit of compost to the hole and fork it in. I've had good success with mycorrhizal fungi sold as "Rootgrow". Useful to add to the hole but not essential. Water the hole- a good watering can full.
Knock the plant out of the pot, you might need another pair of hands at this point. Pop in the hole, check the soil levels and back fill the hole, gently firming with your foot as you go.
You'll need to keep a check on the watering over the summer but I suspect it will romp away now. Good luck and let's have some before and after photos please!

Thank you for the reply, it is in a very large ceramic pot so i cant sit it in water as i cant pick it up, somehow i need to dig it out but i don't want to damage it.

Sounds like you need to invite some friends round to a Plant-a-Hydrangea party!