title: Create upload field in Wordpress plugin
body: <p>I'm starting my first new plugin, and as a test, I pretend to create a field in my plugin admin (back-end) where the user can upload an image, and that image will appear on the header of my main wordpress page (front-end).</p>
  
  <p>My question: how can I upload images through my plugin? And later on, how can I make that image appear in my front-end?</p>
  
  <p>If someone could just head me to the right direction, I'd appreciate.</p>