Calculate minimum gutter fall of 1 50 that is for 2mm of fall for each metre of gutter then put a nail at the lower end and fix a stringline between the nails and check fall with a spirit level.
Fitting internal gutter brackets.
Take the first length and clip it into the running outlet then into the facia board brackets.
Clip the two ends in and fix to the facia with a suitable screw.
Join the next length of gutter to the first with a union bracket.
Having fitted the gutter brackets it is time to fit the guttering.
Guttering is generally sold in 2m or 4m lengths and is easily cut to size with a hacksaw but be sure to de burr any cut surfaces with a file or sandpaper.