How does 'voter fraud' work?

[2ndAmendment]

...there is no way any one individual has access in such manner that they can cheat it, do you trust them, what we used yesterday, as much as what we had before, the paper ballots and how they were scanned and counted?

Judging from what I saw during the primary, I think that is a big assumption.

I'm probably the wrong person to ask today. In a few days, maybe I'll have a clearer mind. Right now, I'm looking forward to the next terrorist attack.