You don't, if you're trying to get the songs for free, that's piracy. So, you want to stay away from Limewire. com which is peer-to-peer, it's piracy too! Look up downloads on Google for sites like ReverbNation, Immem, and Amie Street which have free and dime tunes.
To add music to your ipod without using itunes then you need to use a third party program that is compatible with an ipod. There may be some conversion need also to put them on there also.