Hello,
For text files, do following:
1/ run JUNOS command "start shell"
2/ when in shell launch VI editor
3/ copy-paste text file into VI editor window
4/ save file with your chosen name.
For binary files, there is no supported way to transfer over telnet as it requires UUCP signed binary which is not part of JUNOS software distribution.
Use SFTP or SCP to transfer files. Enaling SSH also enables SFTP and SCP.
HTH
Thanks
Alex