There are 2 very simple ways to get the worms into your soakaway.
1) Remove the septic tank lid.
2) Simply pour the bucket of worms and bedding into your septic tank.
3) Replace the septic tank lid.
4) Within 1-2 days many of the worms will slowly start to make their way into the soakaway, breeding and multiplying as they do so.
Alternatively, If you have a manhole chamber installed that runs directly into your soakaway, just pour the bucket of worms and bedding into it.
Within 1-2 days the worms will make their way into the soakaway pipes.