How to set up Qconfig.py and where is the file? I mean under which folder? Like
The Qconfig file was used to hold your API key, so that you could access the cloud based quantum devices and simulators. For the most recent version of Qiskit, it is no longer required. Instead you can use the command
from qiskit import IBMQ IBMQ.save_account('MY_API_TOKEN')
This is a python command. You can do it in a Jupyter notebook, on the python command line, or wherever else you prefer that accepts python3 commands. You will need to replace
MY_API_TOKEN with the token you get from the IBM Q Experience website.
This step of saving credentials only needs to be done once. Afterwards, you can simply load the saved information using
from qiskit import IBMQ IBMQ.load_accounts()
Full instructions can be found here.
If you still want to use a Qconfig file, you can. You can create one yourself using the template in the link above. Then you place it wherever you want. To import it, using the sys package to append the path to where you have placed the file.