Yep. Python script files cannot be drag and dropped into Rhino (don’t know why it is limited like that, but that’s how it is…) Here are some instructions:
First, here is some basic info from the Rhino developer docs.
Following are some more detailed instructions. They are platform-specific.
For Windows Rhino users:
To run a python script (*.py) from a toolbar button:
Right-click in a blank space in any toolbar and choose “New Button”.
In the button editor that opens, in the "Command area, type the following:
! _-RunPythonScript (
<paste the entire script here>
)
Then OK to exit the button editor. When you click the button, the script sh…
or
https://wiki.mcneel.com/developer/macroscriptsetup