If you want to look into train journeys, look on The Man in Seat 61 website.
For flights, look on a comparison site such as SkyScanner.
If you're planning on making your own way (eg by bike, by car etc), then get a map and plan a route.
For when? right now? summer time? Check out with Easyjet or Ryanair.
All you have to do is Google it - it depends on when?
Also any travel agent will answer that question
on a plane?
on a boat?
on a train?
and - more important - TO WHERE IN SPAIN
