It's quite easy using HomePlug. It's terribly useful if you need to have some sort of network connection but don't have the means to wire it - and perhaps you don't like the idea of a wireless network.
And it is quite easy to use - simply plug in the adapter, and you have ethernet. There's a number of problems though, such as speed (even wireless is faster), and reliablility: often applicances can emit certain frequencies which cause interference with the connection. So it's HomePlug is only useful in a limited number of situations.