To punch holes in paper that will fit a discbound planner, you need what is called an arc punch or sometimes called a discbound punch. These hole punches will punch what looks like an arc into your paper.
I personally use the Mambi Big Punch and love it. You can find them at any planner supplies store like Hobby Lobby, Joann, or Michaels. But there are also arc hole punches available at office supply stores and Amazon.
Before you buy one, I would recommend deciding what system and accessories you will be using first. There may be slight differences in the depth of the hole punch in a MAMBI Punch Vs. a Tul punch. So if you plan to use Happy Planner disc, I would recommend the MAMBI punch.