The Amazon European Fulfilment Network (EFN) allows a seller to fulfil orders from different Amazon European marketplaces at the same fulfilment centre. For example, orders from Amazon Germany and France could be fulfilled from the same Fulfilment Centre as United Kingdom orders. 
To set this up in Linnworks, you must do the following: 

Integrate all the Amazon Marketplaces as different channels. This is so all orders are pulled into Linnworks. Click Settings Open the Config screen for each channel by clicking Channel Integration Enable FBA Sync Inventory for the channel that controls the main FBA location that all your orders will be fulfilled from. Disable FBA Sync Inventory for every FBA channel that does not controls the main FBA location that all your orders will be fulfilled from.