Think of your Mod Podge as a glue and a sealant. I would suggest lightly sanding the surface of the clipboard to ensure that the paper/modpodge adheres well.
1. Sand the clipboard
2. Put a moderate amount of modpodge on the clipboard and put your paper on. Smooth it out with your fingers to ensure no bubbles.
3. Let it dry (15-20minutes, usually)
4. Apply 2-3 light coats of mod-podge over the paper, letting it dry in between.
5. Optionally, if you want a VERY shiny surface, after everything is completely dry, lightly sand with superfine grit sandpaper (it us usally black and doesn't feel sandy at all) and finish off by rubbing some steel wool. This will make the surface so smooth and shiny.