With the Allow users to relate a contact to multiple accounts feature, you will be able to add single Contact to multiple Accounts. This is useful when a business owner owns more than one company, or you have a consultant that might work on behalf of multiple organizations.
To use this option, you need to enable it in Account settings, and under the Contacts to Multiple Accounts Settings section, select Allow users to relate a contact to multiple accounts.
After that, you need to add the Related Contacts related list on the Account page layout, and the Related Accounts related list on the Contact page layout.
If you need to change the roles from the Account Contact Relationship, you can do that in the object Account Contact Relationship object in the field Roles.
Now it’s enough to add the relationships in the Contacts and Accounts.
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