I haven't done it on an XPS but I have on several other pc's and the proceedure is the same. You are either going to reinstall the entire operating system (recommended) or clone the current drive to the ssd. In either case you should do a full backup of the drive *just in case* before you proceed.
reinstalling should be self evident. Go into the bios and switch to ahci mode if you want, save, and power off. Remove old HDD & replace it with SSD. Insert OS disk and boot up the computer. You might have to press F12 to get the boot manager to show if the pc isn't set to boot from cd first. Have your ahci drivers handy if you wanted ahci mode.
Cloning the drive takes a long time but the only ones I have had fail is when coming from Raided HDD's. Basically you attach the SSD to the usb adapter, boot the cloning software and let it do its thing. When done power off and replace the HDD with the SSD. Boot back up. You now have the option of switching to ahci mode for better SSD performance since your HDD was most likely in IDE mode. To do that you force the controller to use the ahci driver (google it) and shut down. Power back up into the bios and change the setting to ahci, save and reboot.