You will need to remove the recoil - either separately or as part of the cowling, depending on make.
Assuming you have replaced the cord (as opposed to tying the broken bit back on!), you need to tension the spring.
There is a video on youtube (not mine, but useful nonetheless!).
http://www.youtube.com/watch?v=trdumQJr3w4
phil_saunders@bigfoot.com
Phil Saunders
September 2008