It's "/usr/share/fonts/nokia/Nokia\ Pure/proportional" inside the folder, there are 3 font files "xxxxxxx-Bold xxxxxxx-light xxxxxxxxxx-regular" after u download the Ostrich zip files, pick whatever 3 fonts you want, and rename it to the exact file name inside of Pure/proportional. My method is to SSH into N9 and copy the original and delete them inside WINSCP and replace it with Ostrich. (I believe just to overwrite them will do the trick as well) Finally reboot your machine, if standby screen/lock screen hasn't been applied, you have to SSH into N9 to change standby, lock screen fonts type within a certain .css file. but that's just in my case though, since I have two fonts type in my system, Chinese and English.
cp /usr/share/fonts/nokia/Nokia Pure/proportional /home/user/MyDocs/fonts/original cp /home/user/MyDocs/fonts/new/* /usr/share/fonts/nokia/Nokia Pure/proportional/
cp: can't stat '/usr/share/fonts/nokia/Nokia;: No such file or directory