Firmware files for DVB hardware usually go to /lib/firmware. On OpenELEC the filesystem is read only. Therefore copy the firmware file to /storage/.config/firmware. OpenELEC will find it during boot.

Ssh into the remote machine running OpenELEC and create a directory: mkdir /storage/.config/firmware

Use scp for the file transfer: scp /home/elektrozwerg/Downloads/<firmwarefile.fw> root@<IP>:/storage/.config/firmware/
Reboot the machine running OpenELEC. Ssh into it again and check boot messages: dmesg

You might see something like:

[   12.382068] dvb-usb: downloading firmware from file ‘dvb-usb-dib0700-1.20.fw’
[   12.518339] dib0700: firmware started successfully.
[   13.019503] dvb-usb: found a ‘Pinnacle PCTV 73e’ in warm state.
[   13.019742] dvb-usb: will pass the complete MPEG2 transport stream to the software demuxer.
[   13.019949] DVB: registering new adapter (Pinnacle PCTV 73e)
[   13.236852] usb 1-2.1: DVB: registering adapter 0 frontend 0 (DiBcom 7000PC)…
[   13.457245] DiB0070: successfully identified
[   13.493124] Registered IR keymap rc-dib0700-rc5
[   13.494702] input: IR-receiver inside an USB DVB receiver as /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.1/rc/rc1/input12
[   13.495026] rc1: IR-receiver inside an USB DVB receiver as /devices/pci0000:00/0000:00:14.0/usb1/1-2/1-2.1/rc/rc1
[   13.495259] dvb-usb: schedule remote query interval to 50 msecs.
[   13.495267] dvb-usb: Pinnacle PCTV 73e successfully initialized and connected.
[   13.495439] usbcore: registered new interface driver dvb_usb_dib0700