Data Import - Setting Primary and Multiple Related contacts

HI Guys,

We have been given rather dirty data by a client where we need to set a primary contact but also related contact for multiple Accounts.

Elliot is the primary contact on multiple accounts but there is also Shelly who is a related contact on Account 1 and account 2 (seen as separate line entries on the data sheet), how do I set both Primary contact and related contact(s) on an account when doing a data import

Thanks