Amaryllis Bulbs are usually planted in a pot and forced to bloom. If you start the plant off indoors you will get a head start by using the warmer temperature of indoors to force earlier blooming of Amaryllis flowers.
Amaryllis is generally sold in soil, or as a kit with soil and a pot. The soil is usually too poor and the pot too small to support a healthy sized Amaryllis plant.
If that is the case the best thing to do is discard the soil or mix it in with your garden soil. The pot can be used for growing something else that is not such a big plant with a heavy flower.
You can buy ready mixed potting soil for containers or mix your own, and plant your bulb in a larger sized pot. I use one part potting mix, one part pearlite, one part vermiculite and one part humus compost.
I believe this is all that’s needed; however a slow release fertilizer could also be added at this time.
It's a good idea to clean off any dead leaves or layers and don't forget the roots that may have died back. Soak just the roots in room temperature water for as long as two hours.
Place a shard or stone over the drainage holes, and then add 1/2 inch pea gravel followed by your compost so that the tip of the amaryllis is level with the top of the pot.
This will leave room to water the plant properly.
Spread the roots out and push down on the bulb just a bit to firm it up.
At this point water thoroughly.
Now add soil to between half and 2/3 of the way up the bulb.
And you're done. The next time you water is when the soil is dry or the bulb stars to sprout.
Watering; less often is better than too often. Place your Amaryllis in a sunny warm location.