If you really have learned all this theory - using all these in practical progressions, then...
I hate to say it but you should be answering these questions yourself. If you can't, you really need the help of a good teacher just to get started.
Perhaps people here will give you lessons though it might take a little time. It's difficult to imagine someone so versed in theory who has not been impelled to try to compose something.
Orchestration is an art and the only way to learn it is i) to study scores against passages of music, "just following the score" isn't enough - you need to study the scores, and ii) apply what you've learned by getting simple things performed by local soloists, groups/ensembles/orchestras - or even software like Finale (far from ideal when you're first starting but better than nothing) - and develop a critical ear.
To find out how orchestral sounds are made you need to develop a good inner ear (ultimately to be able to hear something and know (or be able to work out) how it's done. Again, studying scores, even for solo instruments is really the only way. You can get good books on orchestration that give examples that you should listen to. Some I believe also come with a CD. The Northern Sounds "Rimsky Korsakov" site is a very good start. Study all the examples to find out what's going on.
Unfortunately, musical composition isn't something you can slap a credit card on a counter for and get instantly. It'll take time, work and a lot of frustrations but if you're cut out for it, you'll make progress.
So - how to proceed? Just compose something. Doesn't matter if it's simple. Write for a solo melody instrument like a clarinet or violin. Take off from there.
Good luck!
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