A few months ago I wrote an article on how to import files into TDOS using a terminal program and a null modem connector. Since then I have developed an easier way of doing it. It involves using WRDISK and the process described in Importing Files.
Once you have the files you want in a tape image* you can use EOS/TDOS.COM to import the file from the tape image into TDOS. If you are using CP/M you can use the CP/M utility ADAM.COM to do the same.
*I prefer a tape image because there is 256K available versus the default 160K in a disk image