There may be no greater feeling for a composer than to hear their music played by the instruments, musicians. group, ensemble, orchestra it was written for the first time.
Especially if it is written on paper, or composed within a digital audio workstation (such as logic or pro tools) and then played by live instruments.
It may or may not sound as how you might have imagined but as you develop it is likely to sound even greater than you imagined.
With more experience you will begin to be able to imagine what it will sound like with a group or the instruments it is written for and that will improve your ability.
The path to being a music composer or arranger is a challenging one as there generally isn't one guaranteed way of building a successful career.
It is a highly competitive business.
However, you should not be discouraged as even the greatest composers in history had to battle to be composers.
Often the struggle to be a composer will make your work more meaningful as it can be difficult to hide who your really are when composing or arranging music.
Some ideas are to speak with friends or anyone you hear about who might be making an independent film or short video. Often this can be a good place to begin. Also to attend music industry events to network with people to find out about opportunities.
You can also just self start and keep writing. Great music always finds a place in the world!