I've actually done this last year. Yes, you can plant it in the garden now. Prepare a nice big planting hole for it & add some pine needles. Azaleas need moist, slightly acidic soil, filtered light & good air circulation. Not direct sun or deep dark shade, but partial sun. Under a tree is ideal. Trim off the dead part. I spread some pine needles over the top as mulch. This keeps the soil acidic. You can also add a cup of apple cider vinegar to a gallon of water to give it an acidic base.

How big is your Azalea, how long have you had it in the pot and have you been feeding it at all? I wouldn't recommend planting in the garden if you have a limey soil. Possibly needs repotting into a larger pot with ericaceous compost.

If you want to plant it in the ground you will need to take out a very large planting hole and fill with ericaceous compost. It will not thrive in limey soil.

Precisely!

or plant it with ericaceous compost or beech leaf mould and then you will need to give it a feed designed for azaleas every 2-3 months depending on which brand you buy. its a faff but if you want it in the ground that is the best way forward. if you have pine needles as Bathgate suggests it will help alter the pH.