What is the best program to use when running a tournament? Where can it be found?
If you are talking about pairing programs then WinTD and SwissSys are the two with the largest market share. Googlig those should be enough to find them.
Whichever one you pick, I recommend you read, practice, and become proficient at pairing by hand. You wouldn’t want to be lost if your computer goes down.
Also, you will need to be able to explain why the computer’s pairings are correct (or at least defensible) when players challenge them.
Most people would have said “if”. By saying “when” you pre-empted the otherwise inevitable correction.
'neil, in some of those you will have opponenets who will argue not only whether or not the pairing is legal rp best, but even whether or not the rule is correct.