One advantage to tumblers is that they are more aesthetically pleasing (and less smelly) than compost piles. You can put your tumbler anywhere in your yard that is convenient.
Smaller sized pieces are better. Try grinding or shredding any large materials before adding them to the tumbler. There are many organic things that should not be put into the compost pile, including citrus peels, onions, meat, and fish scraps.
The best way to gauge your carbon to nitrogen ratio is to keep track of the things you put in your tumbler. You can find guides that give you the relative carbon and nitrogen content of different compost materials online.
Instead of continuing to add to the tumbler, you could have a compost bucket (or a second tumbler) that holds scraps until the current batch is finished. Then, you can move the second batch into the tumbler.
Add horse or cow manure to the tumbler. Add garden soil to the tumbler. Add a commercial composting mix to the tumbler. These can be found online or in a garden store.
Turning the composter too often will slow down composting.
If your compost is not getting hot enough, you can add manure or commercial products to increase the nitrogen levels and provide more heat.
Some tumblers unload from the side. Others unload from the top or bottom.
