We received and answered this question via email, but FYI for everyone else: only fields included in the import template can be imported. SKU, BIOS etc cannot currently be imported. We've asked our developers to add these fields to the import code in a future update, but do not have an estimated release date for this feature yet.
Though this is not something we can provide instructions or support for, you could theoretically write a database script and execute it under Configuration\Database Scripts to import the data. SKUs are stored and can be inserted in the tblAssetCustom database table for instance.