Here is a quote from a permit confirmation regarding how to get your permit.

Check-in 1 to 14 days in advance to have the permit emailed.

Visitor centers are issuing all permits by phone and email for the 2020 season. No walk up service.

Check in before the no show deadline (10am) on your entry date.
Print and sign the permit to carry on the trail.
To request your permit by Email (allow 2 days for processing)

In your message answer the following;

Have you viewed the Leave No Trace video?
How you will store your food?
What is your final group size?
Subject line: [Entry Date] Trail Name [Reservation Number]

mail to:

Or call the visitor center nearest your entry trail, or the wilderness permit office:

Lone Pine area; Eastern Sierra Visitor Center 760-876-6200 or 760-876-6222
Bishop area: White Mountain Ranger Station 760-873-2500 (press 0) or 760-873-2503
Mammoth area: Mammoth Lakes Welcome Center 760-924-5500 (press 1)
Lee Vining area: Mono Basin Scenic Area 760-647-3044
Wilderness Permit Office: 760-873-2483 (press 0)