Cut it to length with a hacksaw and removing any burrs with a half round file.
Install gutter downpipe.
Measure in 4 inches from the end corner of.
Gutters over flows add downspout to bring water down from roof faster.
Fit the gutter in place which normally just clips in with the appropriate stop ends connectors and gutter outlet for the downpipe.
Place a step ladder under the area you are installing the downspout.
Watch and learn how and stop.
Drill a hole in the bottom of the gutter at the 4 inch mark with a 1 inch hole saw attachment to the drill.