Secondary fermenting produces smoother, cleaner beer free of yeast haze.
Let your beer stay in the primary fermenter two weeks. The first week the ferment happens, the second a lot of yeast drops out and cleans your beer.
You must "rack" the beer using a plastic tube or hose, no splashing to be allowed. This is most important! Equally important, your racking hose must be well sanitised!
After the two weeks, attach the racking hose to the tap of the primary fermenter and the other end of the hose to be attached to either the tap of the secondary fermenter or, easier, going through the bung hole and resting on the bottom of the secondary fermenter. Turn the tap on slowly, then as the end of the racking hose is covered by beer you can turn the tap on a bit more. No splashing of the beer though.
The secondary fermenter must be a foodgrade 22L container so when your beer has been all racked into it there is very little airspace or ullage. The air in the oxygen will spoil the beer so ullage must be minimised.
Chuck the secondary into a fridge set to .5C and leave it there 2 weeks for a kit beer. The very cold temp "lagers" your beer so your ales and lagers are cleaner. The low temp also causes more yeast to drop out, which is good.
While it is in secondary you can indeed dryhop ales. Use whole or plug hops for this, good quality hops like Fuggles or Goldings, etc
When racking the beer back into your main fermenter (now being used as a bottling bucket) you can bulk prime your beer, preferably using about 1/2 cup of wheat dried malt extract dissolved into 1/2 cup water.
With 2 secondaries you can have 3 beers on the go
Tom Smit