Merging ASP.Net Identity DbContext with my DbContext

I'm using the default ASP.Net MVC template in Visual Studio. I'm using the ASP.Net Identity code that was created for me in the template. I'd like for the DBContext I use to be aware of the relationship between the ApplicationUser entity (AspNetUser table) and the rest of my entities. For example, I want to be able to have an ApplicationUser.Messages property that exhibits the relationship between the ApplicationUser and Message entities. I have my DbContext for all non-Identity entities in a Data Access Layer project. And the template ApplicationDbContext is in the UI Layer. In order to keep the relationships between the Identity entities and my custom entities, I need to merge into one DbContext, right? How do I do this? I'm using the default ASP.Net MVC template in V