Python doesn't support Windows Forms. Winforms is a NET technology. Please provide the instructions you're following to do this so we can understand what you're doing.
Visual Studio does support Python and developing Python apps using standard Python frameworks as discussed here. To support Python in VS run the VS installer, go to the Individual Components
tab, type python
in the search box and select the Python components. This will add the necessary support for working with Python. AFAIK you don't need any additional VS extensions for basic Python support. If you installed additional extensions then ensure they don't get in the way.
If you want to be able to call Python in your .NET (winforms) app then you'll need a third party library that adds support for Python in .NET. IronPython used to be the way to go but I don't know anymore. PythonNet seems like a more recent solution. It does support "loading" NET into Python but I suspect you're going to find it limiting. Also note that VS doesn't provide support for any of this so you'll access to features like WYSIWYG editing of the UX, etc.
In general I would recommend that you use the best language for each task. Since UX stuff is easier in C# then build your Winforms app in C#. If you have existing code in Python that implements functionality then have your C# app call the Python logic to perform the actual work of the app and leave the UX functionality in C#. But that is just my opinion.