First, let's see how to mount the remote directory. Assume that there is a shared folder over the network at \\192.168.1.1\users\self\shared which is accessible with user myuser and password secret123.
We could mount it manually in /mnt/winshare with:
# mount -t cifs //192.168.1.1/users/self/shared /mnt/winshare -o user=myuser,password=secret123
This should work on your Linux box, because systemd will basically call mount with the same arguments: What (//192.168.1.1/users/self/shared), Where (/mnt/winshare) and Options (user=myuser,password=secret123).