ASP.NET Identity and Entity Framework Database-First Approach

I have used ASP.NET Identity in my code-first projects before and tried using it in a project that has an existing database-first approach in MySQL.

I have gone through almost everything I could find on the internet to make this work, but failed with errors like missing key or changed entity at runtime. I must be missing something here.

I would be really grateful if anyone gave me a comprehensive guide to implementing databse-first with ASP.Net identity. Thanks!