Here is the link to our API documentation (you should be able to access dev portal with your Linnworks credentials)

1. In dev portal create System Integration application. 

2. Install it on necessary Linnworks account using installation URL - provided in dev portal.

3. On installation you will receive token - static parameter that you will have to pass with application Id and Application Secret (both visible in dev portal) to this call

5. Update shipping information of open order -

7. If you want to get more detailed information about open or processed orders -

8. Adjust stock levels:

9. Getting the list of available locations and their IDs -