Remote Update over PCI Express

If you open up the MegaWizard Plugin-Manager, find the "ALTREMOTE_UPDATE" core, set a directory to generate the core to. After clicking next, the actual wizard for ALTREMOTE_UPDATE will launch. Here you will find a "Documentation" button on the top right, which links a couple of manuals on the topic for various parts. That should get you started.

The core does not help get a bitstream from PCIe into the flash chip - you need to solve that on your own. It simply provides a way to tell the on-board configuration logic to use an alternative base address for the next configuration load, and to cause a reconfiguration event from user logic. You can also separately use the core watchdog functionality, to cause a reconfiguration if a particular part of user logic locks up.