Gotta learn theory
Jazz:
Get a book on "harmony and music theory" and study it.
The topic is dry and confusing at first, but there ain't no shortcuts. You have to put in the time.
As you read the stuff, you MUST solidify and internalize your new knowledge by applying it EVERY DAY. Here's how:
First, LISTEN to some music that you consider "jazzy". Even a pop or rock or TV commercial that has a "jazzy" sound. Analyze that music into its components. You must constantly strive to understand music in terms of its basic harmony elements. You become a jazz player by distilling down music to its basic structure, then re-building it with your own decoration. Distilling is not foreign to the jazz musician: you can also distill your own bourbon if you want to emulate the original jazzists!
Next, PLAY a short jazzy ii-V-I progression (for example, Ami7, D7, GMaj7). Use that as a basis for exploring the dissonant tones of jazz by employing substitutions. Some possibilities are:
Ami7b5, D7b9, GMaj7
Ami7, G#, GMaj7
D7sus4, Dmi11, G
Cmi6, Ab6, GMaj7
Ebmi7b5, Ab7b9, DbMaj7
As wacky as those examples may appear to be, don't be intimidated by the letters and numbers. They are all just "jazzy" ways of playing the standard ii-V-I progression. In fact, each of those examples can be thought of as: Ami, D7, G with extensions. However, it is precisely those non-scale extensions that make plain chords turn into "jazz."
And that leads to the topic of SCALES. Jazz is about simultaneously embracing and ignoring scales. It's all about scales, yet nothing to do with them! I like to use scales as a way of describing what is played, rather than prescribing what to play. You need to master various patterns of notes on your instrument in the form of scales, arpeggios, and intervals. Scales are but one pattern, and are used as a framework for developing more complicated melodic lines. But that is just the technical aspect of jazz. And if you are merely a technical whiz, you'll succeed in boring your audience unless you shape that wizardry with ideas.
Lastly, IDEAS come from listening. Listen to others AND to yourself. Don't pick one dude to copy, nor one genre to specialize. Your success as a jazz musician will come from your ability to blend styles into your own unique sound which captures and entertains!
Now, 'scuse me while I enjoy my [freshly distilled] bourbon!
/F