Only 64 people per day get to hike the wave.
There are two ways to get a permit, both by lottery via Recreation.gov. Enter four months (higher odds) or three days in advance.
The Wave lottery three days in advance requires you to be physically in the vicinity (remote northern AZ or southern UT)
Fortunately, there are a ton of other bucket list-worthy things to do near The Wave Arizona, so you can make it into a bigger trip even if you don't win a hiking permit.