At this point I’d plant it right in the ground in a wind sheltered area, morning sun, afternoon shade. (See final note)
Please do not prune the roots right now. You can lightly prune the top to remove any suckers though.
I’d recommend using 50% sifted fine fir chips, 25% Peat and mix in 25% soil or less.
If you have a clay layer that you have to dig into, don’t, it will prevent drainage and create a bathtub that will kill your azalea.
In this case, Instead plant it above the clay layer using more of the mix to build up your bed around the azalea for about a couple foot around the plant.
Finally put a ring of chips about 2” high on the surface just outside the drip edge of the rootball.
If you don’t have a wind protected space, create a 360 wind barrier around the azalea.
Also, remember that all USDA zones are created alike. For example, your climatology is not like a similar USDA zone in Alabama, even though your low temperatures may be.
All my recent azalea purchases (40+ to date, although my better half says there are 100s!) are dug in the beds inside my cold frames to protect from wind, pots and all. Then I’ll pull them in 2021 and decide which get pruned and planted in ground and which go in oversized pots. You could do this if you have a similar set up.
Finally I’d download the edited Guide here vs your version
cheers
DSD sends
PS: Feel free to PM me if you have any questions.