Working with unreal editor from source build dedicated server/editor

I am following a youtube tutorial on creating a dedicated server and a was wondering a few things. When i try to open the project with the source build. I get an error saying can not launch editor.

And for the source build for a dedicated server, do i need to include(create a folder) for the Marketplace plugins? If i do will building the engine detect the added folder or do i need to include it somewhere in the code?