Test the community version of Unity.
The current technique is to use a Skybox.
My older tutorial used an inverted sphere.
This is 4 years old. It may no longer work. Also, the flip-normals sphere is not the best practice now. As the recommended approach is to use a Skybox as shown above. However, if you want to just get things going, the inverted sphere may work.
The camera should appear as a webcam inside of Unity.
This likely no longer works, but it help as a reference.
Post again if you get stuck or have more questions.