How to sell Nikia Lumia 1020 on eBay?

I bought a new phone at an ATT store and they wiped my old phone. I went through the unlock process on the ATT web site and it was approved (see below). I'm stuck at instruction "3", insert a non-ATT SIM card. Never did this before. How do I reconcile these instuctions with putting the phone up for sale on eBay as "unlocked"? Thanks in Advance.

Device unlock portal - Approved

We’ve approved your request to unlock your device. Here are the instructions to

complete your unlock:

The unlock code is (I erased)

Ten unsuccessful unlock attempts permanently locks the device to the

AT&T network.

1. Switch the device off.

2. Remove the AT&T SIM card.

3. Insert a non-AT&T SIM card.

4. Switch the device on. If prompted, enter the SIM PIN code.

5. Wait for the SIM unlock window to open.

6. Enter the unlock code provided (8 or 20 digits) and press Enter.

7. Power the device off.

8. Power the device on. The device is unlocked.

IMEI Number (I erased)

Request Date/Time 10-26-2016 19:20:47 PM

Request Number (I erased)

Current Status Approved