They are complicated...all due to Merced County's COVID19 status as determined by the the State of California. It's purple--the highest rating. So they are being extra careful.
You'll need a reservation to enter the park, a reservation for a campground, a reservation for a wilderness permit...and each of those is a little different.
Here's a link to the whole schmear: https://www.nps.gov/yose/planyourvisit/covid19.htm?fbclid=IwAR2FQg_QHvkaw1WyD7msyEZRX0BrPZSSW1D1aJtxRr9Mp1qL33JETlFtHsY
Of course, all of this may change the the middle of June, when the state expects us all to be out of the purple and red tiers. But that also requires a lot more vaccinations, and right now, there is a shortage of the vaccine in California. Crazy times.