Assuming your PC is compatible but Miracast isn’t working, you may need to install/ reinstall the Wireless Display optional feature. This is the legitimate “download” process.
On some Windows 10 installations, the Connect app or wireless display feature may not be installed by default. To add it: download miracast for windows 10
Once installed, you can launch the Connect app from the Start menu. Assuming your PC is compatible but Miracast isn’t
Do you want to project to your Windows 10 laptop from your phone or another PC? You need to enable the receiver settings. Once installed, you can launch the Connect app
On some Windows 10 versions, you need to add the Miracast receiver feature manually.
If the steps above didn't work, or if your PC cannot find your display, you may need to perform a few "downloads" to fix the issue.
dxdiag