When entering the Media Manager you can clock on "Configure Devices - Configure Color Sampling Devices - (Button) Manage". In the window where the installed measurement devices are shown you could (Button) "Add..." an additional one.
In the list of available devices you will find "HP Designjet L26500", if it's installed at the computer you try to calibrate. After selecting it and clicking on the button "Continue" (should be, I use the german version) the available Ports are shown, in this case TCP/IP only. If clicking again on "Continue" you will be asked for the IP-adress of your printer.
After clicking on "Continue" again you will be asked how many times you want to measure every swatch. After that you can Click Finish and the L26500 is added to the Measurement Devices List.
The printed color samples for measurements are very large, if you do that more often it will be better to buy a separate i1, because this will read much smaller swatches, it will not waste so much material. But using the printers i1 is really comfortable because it will print and read all swatches automatically.