There are two ways of creating new items in your Linnworks inventory:

• Creating items manually and one-by-one.
• Creating items in bulk via import

If you have active items on your integrated Sales Channels and want to create inventory based on the details on the channel, then there are options for this as well depending on the Channel you are using and keeping in mind certain limitations. 

A short overview for the options for creating inventory items based on channel items is available here.