Welcome to the forum Susustra!!
To plant a bare root rose you must first take the rose out of it's packaging and put it in water to soak for several hours.
While this is happening you can prepare your hole. The hole needs to be about 2 feet deep, and 2 feet around. With the soil you have removed, mix in some soil amendments to provide more nutrients to your rose. These could include compost, well rotted manure, bone meal, shredded leaves, alfalfa pellets, and epsom salts.
Take some of this mixture and build a small mound in the middle of the bottom of your hole. Now your hole is ready.
Your rose should be trimmed of any dead wood, and any broken or diseased canes.
Place your rose in the hole with the roots fanned out over the mound in the middle. If you have purchased a grafted rose, you need to ensure that the bud union is just level with the ground if you live in a warmer climate, and if you are in colder climates, ensure that the bud union will sit at least 4" below the ground level.
Now backfill your hole with the remaining soil mixture you have made, gently packing it with your hands. Do this in stages, putting some soil in, then watering it well to help it settle, then put more soil in, then water, until your reach the top. Don't stomp down the soil, as you may break the roots. This prevents air pockets being left behind to then make everything settle, or bacteria to begin to rot your roots. You should leave a 1" well around your rose, so that water will not run away from it when watering.
If you like, you can mulch around your rose to assist in keeping the roots at an even temperature, and slow down the evaporation of the moisture in the soil.
Now wasn't that easy!!!
As for where you can find your Sally Holmes rose, I am probably not much help there, as I live in Canada, and don't know the suppliers down there.
Can anyone else help with this?.............
Hope you enjoy the forum susustra, and feel free to come back anytime with questions, answers, or just to chat!