There are three components that are required to be download: The Quartus setup file, ModelSim setup file and the device setup file.
Click here and you will be redirected to the download page. Download instructions are given below.
Choose Software Type as FPGA Development, Software Package as Quartus Prime Lite, Version as 20.1 and Operating System as Windows.
If you scroll down, you will see the Downloads area. Under the Individual Files tab, download both Quartus and ModelSim setup files as highlighted below.
If you scroll down further, you will encounter the list of devices supported. Download the Cyclone IV device support file and save it in the same location where you stored the setup files from the previous step.
Make sure both the download files are stored in the same directory (preferably the Downloads folder) on your local disk. Do not use cloud storage.
Next step is to install Quartus and ModelSim. Click here to proceed.