If you're not sure which design program you should use, consult this infographic. It'll quickly guide you to either InDesign, Illustrator or Photoshop, which are the programs most often used by professional designers. It's not 100% foolproof but should guide you in the right direction!
If you'd like a free pdf of this infographic please click here.
If you're completely new to design, try out free ten day Accidental Designer course.