Go to [settings] -> [system] -> [General]. The uploads directory path should be shown there, and should be writable. You can change it whatever you like, but by default we recommend having it above a web-accessible directory, so if Blesta is installed at /home/user/public_html/billing/, then the uploads directory can be at /home/user/uploads/ and the system directory where you place the GeoLiteCity.dat file would be at /home/user/uploads/system/