I usually setup a new solution so that it contains multiple projects. There's a project for web files, data files, services, utilities and so on. When I downloaded and setup Entity Framework through Nuget I installed it into my Project.Web (where all my views/controllers are) and to my Project.Data (where my data context is located with my repositories) projects.
I installed EF Migrations to my Project.Data project as this is where my data context file lives. Everything compiles and run but sometimes when using Entity Framework Migrations I noticed that I was getting an error:
Could not load assembly 'Project.Data'. (If you are using Code First Migrations inside Visual Studio this can happen if the startUp project for your solution does not reference the project that contains your migrations. You can either change the startUp project for your solution or use the -StartUpProjectName parameter.)