I planted my begonia two weeks ago and they are now popping their heads out of the surface --up about 1/2".
When planted, their tops are placed just under the surface--barely. When they first begin to show, you'll notice what looks like a bit of fuzz at the surface. That's them. So don't brush that away.

Mine are enjoying an eastern light--the cool morning light that I have to use---the only other light is a western exposure that currently has my Christmas Cactus and is fostering its bloom. Since they will not go out of doors until well into May/June, they have plenty of time to promote themselves.

The first watering is to drainage and the excess in the saucer is dumped. Thereafter, I keep the surface damp---but not soggy. We don't want to rot the bulb.
This is their 4th year....and I still haven't learned to try to identify them of their color before I store them so every spring its a learning process of which color is in the pots.

Many begonia and bulbs of their ilk, start out life ontop of the refrigerator. The heat there is just right to prompt early growth.

In the fall, let them be touched by frost which will wilt their leaves. That's your cue to lift them, brush the soil off, put them in the garage or shed for a day or so to dry, then store them in a cool, dry, dark location where they sit idle until ---well, until about mid March when we wish them to grow. If you have geraniums--pelargonium that is, the same storage is given them and they too can be brought out at the same time to start life anew. They are just not allowed frost before storage.

I have had good luck with them in a 25% peat moss/potting soil mix. The peat moss holds moisture without going overboard on their watering.
Using a too easy potting soil or soiless mix can, I think, prevent their staying damp and prompts more watering.