When in this mode the kb article referenced above is pretty much the only option.
https://kb.juniper.net/InfoCenter/index?page=content&id=KB5519
you hit the enter key during this prompt
Hit any key to run loader
Hit any key to run loaderHit any key to run loader < Press the 'Enter' key at this point
Then follow the steps in kb from there. You do need a TFTP server on your laptop and this connected to the device with the files for the process installed