My training routine was

Jog 400m followed by a quick 400m as a warm up
Then
1 Sprint 100 walk/jog 100 Repeat 8 times
2 Sprint 200 walk/jog 200 repeat 8 times
3 Sprint(well sort of) 400 jog 400 repeat 4 times.
4 run 1500 steady pace.
5 jog 400m or so to cool down.

this works out at about 10k.

keep a note of how long each section takes and once a month make a big effort to reduce the time taken for the whole set.

Alternate this with an even paced distance run of 10k and have a rest day each week. Dont forget to measure your time for the even pace run.
Worked for me.