Which product should I use to clean my laptop screen?

Hi @pptchh welcome to this free user to user Alienware laptop discussion forum. 

Moisten a microfiber cloth with a mixture of 70% isopropyl alcohol / 30% water. When cleaning a display screen, carefully wipe in one direction, moving horizontal from the top of the display to the bottom. 

Guidance for Keeping Your Dell Technologies Equipment Clean 

Dell Laptop Best Practices for Care, Use, and Handling 

A bit of Windex sprayed onto your microfiber cloth will certainly get the job done. But remember, never spray the Windex directly onto your laptop screen itself. If you don't have a microfiber cloth or a sponge fresh out of the package, a soft duster brush will work.