What you get in the mail is your reservation. AFAIK, you must pick up your permit at "a" ranger or the park office on the day of your entry ... or sometimes the day before.

They sell fishing licenses and outdoors cards at the stations or you can get them in advance from all sorts of places to save time. Again, that's a different government agency.

To get a park permit you have to physically show your smiling face or put your money in an approved pole out of season.