You will need an ftp (or scp) server that the sensor can log into and be able to place files on.
If it is just the config you want then:
copy current-config ftp://user@server/directory/config.txt
However, the TAC usually wants a full diagnostics report (which includes the config):
show tech-support destination-url ftp://user@server/directory/techsupport.html
(The output will be downloaded as an html file)
If you don't have an ftp (or scp) server available then the other option is to run IDM. There is a diagnostics option in IDM that will bring up a similar html file as above. You can then select the File->Save As option in your web browser to save the html file and send it to the TAC.
