How to customize ASP.NET identity with my own user table

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ASP.NET4

identity-server-4

I have an asp.net mvc 5 application with individual user account security extended with user roles and centralized user administration (users can't create accounts, only application administrator, i.e. me, create accounts and assign roles to them).

My user class looks something like this:

public class ApplicationUser : IdentityUser
{

// User name, full name, e-mail etc....

}

and it's stored in "AspNetUsers" table provided by identity...

Now i need to expand this by adding CompanyID property to a ApplicationUser class and new table with company informations (already existing in database)...

Can someone point me where to find informations how to do this?

What I have tried:

everything is working fine now but i need to put the user data into the aspnetuser table , but in my case i have registration table where my users are placed . so how i can use my own user table to join with roles table of identity rather than user their aspnetuser table