Clip the two ends in and fix to the facia with a suitable screw.
Fitting internal gutter brackets.
Take the first length and clip it into the running outlet then into the facia board brackets.
If you live in an area that is prone to regular heavy snowfalls position fascia brackets so they are no more than 400mm apart.
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.
It s easier to start by clipping in the back first.
Join the next length of gutter to the first with a union bracket.