The download process depends on which agency processed your application. You can find this on your application receipt.
If you applied through the Protean portal, follow these steps: What is e-Pan Card, Apply, Status and Download - ClearTax download pan by application number
While many refer to it as an "application number," the official term used for downloading is the (for NSDL/Protean) or Application Coupon Number (for UTIITSL). How to Download PAN by Application/Acknowledgement Number The download process depends on which agency processed