The base of the winch must be higher than the sheet elevation, so that the sheet rises towards the winch. This should be between 3 and 8 degrees below the winch's perpendicular axis. Ideally, the winch's output gear
should be about in line with the angle of entry.
If the sheet enters the winch drum horizontally, or from abobe, a wrap is inevitable.
With a proper lead-in angle, you should be able to fully load (or very nearly so) the drum.
The photos are less than ideal examples, as the left pic shows too steep a rising angle, and the right pic shows a gimpy set-up (about correct angle).