There are two ways you can do this.
Run the ZCL Electrum EXE file, and choose to create a new wallet. If you already have an existing wallet, but still want to create a new one, type a new name for the wallet, and press next. Once you're on the next screen, select "Import Zclassic addresses or private keys".
Copy and paste your private key in the text box on the next screen. Do not use the file locator tool in the bottom right corner.
After clicking next, your address should be imported.
Create your new ZCL wallet if you don't have one, and then click "file>private keys>sweep". This will incur a small fee, and will pull in your ZCL to a new address. It is important to note that this method will put your funds to a new address. This would interfere with things like the mining donation pool.