I want to add ssd to my laptop , is it possible?

Hi,

You can replace the HDD with a 2.5" 7mm sata SSD. Ensure that the SSD you get comes with a 9.5mm adapter. The adapter is just a spacer that is placed below the SSD to raise it to the correct height so that it plugs into the laptop's sata port correctly.

Here's the ifixit HP Envy x360 15m-cn0012dx Hard Drive Replacement guide that will help.

Here's a link to just one supplier that shows what SSDs are compatible. There are other suppliers that may suit you better.

Also most reputable suppliers provide access to cloning software and information with their SSDs so that you can have a seamless upgrade from HDD to SSD.