assuming it is the correct line, correct shape / length, with correct fixings....

get a blowtorch, and a bed of dry sand, heat the sand in an oven to 200 celcius, takes an hour, pour some of the sand in a container, heat the whole line cherry red, put it on the sand, cover with the rest of the hot sand, leave three hours to cool.

clean outside of pipe with emery tape, clean inside from both ends with 100 psi airline, do each end three times, then flush through with clean diesel.

fit, finger tight both ends, should BOTH nip right up with fingers only if you have the right pipe and shape, tighten IP end last flat or two, run engine till pipe bleeds and tighten injector end last flat or two.

job done.