How to generate EDMX file for EF6 in ASP.Net5 (Database first approach)

I am trying to use EF6 is my ASP.Net5 application, I installed the package from Nuget but I am not getting any template to generate the EDMX file. I found couple of article that talks about code first approach.

But how can I use DB first approach with EF6 and Asp.Net5, because I already have my database design ready. Can someone help me out here.