Very little is required. I shoot black powder out of a number of single shots and only occasionally out of my Marlin 1895 Cowboy.
With real black powder (black powder substitutes are different), you can simply load as you would with smokeless, except fill the case to the bottom of the bullet with FFg and seat a relatively soft bullet lubed with a black powder compatible lube.
Complexity can go up from there as there are some subtleties when it comes to putting together the most accurate load, but it is just that simple to get started.
Here is a link to a nice intro to black powder shooting, although it's geared more toward single shot BPCR shooting.