String manipulation.

Hello. First of all I am a beginner in Haskell, and I must confess I do not yet fully understand it. I need to write a program in Haskell, though, and I am having some difficulties... What I would like to ask, is how can I take a string from a list, and manipulate it, in order to convert it to an integer. Any help would be very appreciated. Thank you very much, Dimitris