Alan Dershowitz discusses that in his book. You have the Chief Justice presiding over the trial and the senators are the jurors.
Managers appointed by the House are prosecutors and the President has his own defense team.
If we go by the Clinton precedent, it will be a short trial. Since Democrats don’t have a case, its entirely possible Trump may just rest his case.
If he decides to call witnesses, it could be a long trial.
"If" nothing. The entire advantage of the fraud impeachment would be to call witnesses at a senate trial.
That's where they get buried and the house of Biden falls, as the houses of Bush, Clinton and Obama.