Where can I learn to write film scores/symphonic music?

I currently am writing a song in garageband. I have taken guitar lessons for nearly 3 years and have had lessons in music theory. But I have discovered my true love for music is more composing rather than playing, so I am putting my efforts into learning how to write good film scores or symphonic songs. Are there any websites that could help me along? Or any tips you can give me? I really appreciate it. I just want to begin to have others and myself enjoy what I write! Thank you :)