First of all, great that you want to learn to compose!
I can share my composing advice.
When I started to compose, which is circa 2,5 years ago, I did not know anything about music theory.
I did play saxophone and I learnt to play keyboard. So, I was familiar with reading notes and chords, but harmony, form, counterpoint etc. were terms I never had heard of.
To be clear: my first compositions were garbage, but I am so glad that I wrote them.
Every 'mistake' you make, will help you with composing the next piece. Experience and doing it is the key.
I started to imitate and copy Mozart's first minuets so that I became familiar with standard forms and harmony.
Furthermore, I listened to all kinds of music.
Since you say that you already have some knowledge of theory, I think you should just start composing.
When you do not like the result, do not delete it, but look why you do not like it and what you could change so that you will like it.
Good luck!