Your question is rooted in a bigger question.
That you have imported a file, doesn't mean you have it available in this microflow.
You need to pass the file or retrieve it in this microflow before you can model the further process.
This action requires an object of a (specialization) of FileDocument. If you don't feed the file to this action, the action isn't configured correctly and you get this technical error
Answering the next question how to get the file in this microflow: that's depending on what you already have modeled, what the process is, what the objective are etc...
So in short; first you need to think out the process, then model it.
Hey Rene,
Thanks for the assist :)