First, Install the nano text editor:
MINGW64 ~ $ pacman -S nano
Open the File /etc/pacman.conf :
MINGW64 ~ $ nano /etc/pacman.conf
Add the following lines at the end of the file:
[odfi]
Server = http://www.opendesignflow.org/packaging/msys2/$arch
SigLevel = Optional TrustAll
Save the file by pressing CTRL+X, then press Y to accept the changes.
Now run the command to update the list of available packages:
MINGW64 ~ $ pacman -Syy
MINGW64 ~ $ pacman -S odfi