How to import and create a Multilevel BOM directly in erpnext

We have a standard BOM format containing 10 fields in an specific order. We need to import it directly into the BOM in manufacturing. Please help in this regards.

I tried doing with creating a customized Doc Type but wanting to know how to link the items to the master Item List.

You can add Custom Fields in BOM Doctype, and use the Data Import Tool.
If your custom fields are in BOM Item Table instead you can customize the BOM Item Doctype using the “Customize form”:

However I would advice you to only add custom fields if there are no existing fields that satisfy your requirement.

If you have a custom field in Item Doctype that you want in BOM Doctype, you add it as a “Link” type field.