Yesterday i just switch from lubuntu 15.04 vivid vervet to lubuntu 15.10 wily werewolf, so now my laptop runs lubuntu 15.10 for daily use.
You can either upgrade straight from 15.04 to 15.10, or you can also do fresh install of lubuntu 15.10, fresh install means your current data will be erased.
For me, i prefer doing fresh install, so i download the ISO image of lubuntu 15.10 and then create an usb stick installer (live usb stick/drive).
To create the usb stick installer (live usb stick/drive) you can use program like universal usb installer (windows only) or unetbootin (available for windows, linux and mac).
Lubuntu 15.10 is still using LXDE as the desktop environtment instead of the LXQT desktop that everybody is waiting for.
But it's still very exciting to try out, i highly recommend for those who are still using the old version of lubuntu to upgrade to lubuntu 15.10 wily werewolf.