How to plant my memorial rose

It needs full sun and good quality soil.
As soon as it arrives put it to soak in a bucket of water.
Dig a very large hole, the bigger and deeper the better.
Mix the soil you have dug with lots of organic matter. Your local garden centre can recommend a suitable product for your soil type. Buy a stake if you don’t have one. It can be wood or metal.
Hammer the stake really deeply into the base of the hole.
Place the rose bush stem next to the stake and tie it loosely with string or a stocking. You need to wrap the ties in a figure of eight so that the stake is in one compartment, the stem in another. This is to stop the rose rubbing against the stake.
Spread the roots out if possible.
Start filling the hole up with the enriched soil.
Make sure the roots are covered and the tree sitting at the same depth as it was grown. Make sure there are no air pockets between the roots. Sift the soil between the fibrous bits then water well. Even if the soil is wet. The water will help the soil to work it’s way between the roots. Finish filling the hole and firm the soil well. Do not allow grass or weeds to grow around the tree. You could mulch with the soil improver. This means placing a layer of the soil improver in a circle round the stem.
There is no need for fertiliser until late spring.
Make sure it never gets totally dried out in the summer, especially in the first year.
I hope the beauty of the rose brings you happy memories.

I think Esspee has said it all.
I'd just add that roses do like a clay soil but enriched with organic matter.

I put a top dressing of manure on our roses in spring; this year we bought manure in bags from the garden centre. However, it won't need that yet.

In my experience roses are pretty hardy. We had a very narrow (12 inches) garden against the house with some roses growing, they were exposed to most weather. We built a verandah onto the house and the garden bed stayed but was sheltered from all weather. We occasionally watered them in the summer and we fed them and pruned them twice a year. They were never without blooms other than just after pruning.

As mentioned dig a hole bigger than the spread out roots and mound up the centre of the hole so that the plant is higher in the middle than the centre.

Your winter and weather generally is a lot cooler than ours so it may need some protection from the cold until established.

Agree with callistemon about clay soil, also that esspee has given good advice. A half standard rose is best in the soil in my opinion, gets too big to sit comfortably in a pot. I’ve just looked up this variety, it’s a beautiful rose, said to be healthy with a long flowering period so no matter if you aren’t a gardener a good choice. Please don’t worry too much morethan. It will be a beautiful memorial to your much loved daughter in law.

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Well I’ve planted it. Thank you for your advice. Fingers crossed it takes. I’ll take a photo next summer if it does. It hope it’ll be as beautiful as our lovely girl. Thank you

I hope it will bring some much-needed joy to all of you next summer and for years to come.

Hello, your DIL is stunning. Such a beautiful smile. My sincere & heartfelt condolences for your family's tragic loss.
Esspee (above) has offered good advice so follow that & all will be well. Start watching the gardening programmes & speak to anyone you see locally about their garden, gardening in general & what works for them. Gardeners love to share advice. Join a local gardening club & maybe buy a book or two? Monty Don on BBC Gardener's World does say "roses are as tough as old boots". My garden is in quite deep shade (caused by my neighbour's massive Tulip Tree) but my climbers and ramblers do well. Your DIL would be proud of you. Big hug.

DH always says to 'heel it in' because if we have high winds it could rock and disturb the roots.
So just firm it in with feet rather than hands.