You mentioned "down the barrel" so I'll start from scratch.
You load into the cylinder, there is a open area for this. First pour in the powder charge. Until recently this was always done directly from a flask. The flask ought to have a measure on it. Put the tip of your finger over the end, turn the flask upside down and open the valve and pour a charge into the measure. Release the valve and then pour the charge into the chamber.
UPDATE: today a lot of safety conscious people take one more step, they first pour the charge into a separate measure and then pour that into the chamber. On a long barreled rifle with a lot of fouling there is the chance a live ember remains in the bore, there ARE documented accounts of people pouring from a flask down the bore of a LONG RIFLE and having the charge ignite which then goes up the bore and blows up the flask- often fingers are blown away. I have asked a million times if anyone has any evidence this has happened on a cap and ball revolver- still waiting for some documentation- all I get is more of the long rifle incidents. So....do what ever is comfortable for you on a cap and ball and always use a separate measure on a long rifle or even a single shot pistol.
Next, seat a lubed wad over the powder.
Then seat a ROUND Ball over the wad. There must be NO AIRSPACE between ball and wad, ram the ball all the way down on the wad. Lots of folks can sense the powder slightly crunching as this is done.
That chamber is now finished- repeat for the other chambers.
Put a cap on every loaded chamber. Flash heat will go down an uncapped nipple on a loaded chamber and explode that chamber. The caps should fit tightly and not fall off from recoil. If the caps don't fit the easiest solution is to buy a new set of nipples.
Now...this procedure works but you are going to get confused because there are other things some folks do as far as lubing the ends of the chambers, using a filler, etc. For now, just do it as I've pointed out and worry about all the nuances after you've done some shooting.
I'd buy two screw drivers and very slowly hollow grind the thickness and then grind the width so they exactly match the slots on the screws. NO WOBBLE of the screw driver in the slot. Then lightly polish the edges of the screw driver. Grind one for each type of screw (large, small) Two is usually what are needed. Don't use these screw drivers on any other item- only the revolver. You will never have any chewed up screw slots on the revolver- I have one that's over 40 years old and still looks like new.
After a shooting session I completely strip down my revolvers and wash them in hot soapy water to keep them corrosion free. The first time you do this write down where everything goes- after a few times you'll be able to do it in a minute of two. I have a pizza pan I use to set all the parts in while cleaning.
Ask questions if you have any confusion on anything.
Before each shooting session swab out the bore with rubbing alcohol- the oil will turn into a brown tar that can be hard to clean and snap a cap on each nipple to burn off any oil in those areas- then start the loading procedure.