These instructions apply only to a first-time flash with the OEM firmware still on the TL-MR3020 v1 or TL-WR902AC v1. For the TL-MR3020 v3, the instructions are here. If you need to update your HomeTunnel firmware later on, please use the sysupgrade image from this link and start the upgrade from your HomeTunnel local admin interface.
Here is the link to the HomeTunnel factory firmware.
We recommend to print out the slides for reference, so that you do not need to switch back and forth in your browser. You will lose internet connectivity during the process, so if you accidentally close your browser window, you will have a hard time to check back here.