These are the requirements...

1) You need to have the right kind of mind or brain to do this.
Many players I've met and taught can play chords and sing. Many of them can play fingerstyle but for some reason only a few are interested in soloing and, out of them, not many are any good at it.
I think you need to be the right type otherwise it won't work.

2) You need a natural flair for it.
This goes with the above. If you've got the right kind of brain you'll probably have the talent also.

3) You've got to be really interested in it.
You've got to WANT to do it. If your interest is only half-hearted you won't work at it. You've got to work at it and you will work at it if you're interested.

4) You've got to absorb the style.
You've got to listen to what other players do and how they utilise the notes. You've got to study the style, immerse yourself in it, absorb it. If you don't do this you'll never learn to speak the language properly.

5) You've got to start simply and work up.
Quite a few players are 'wannabes'. They see themselves out in front of a crowd, sweating, playing like a genius, but when it comes to having to sit down and go through things, really learn them, they lose interest and give up... which means they're more interested in being looked at than the music.

Good players are interested in what they're doing for its own sake, not fame. They're willing to admit they don't know and aren't very good but they begin at the beginning and work up. How long it takes isn't the point, they just start and make progress.

6) A little goes a long way.
Success breeds success - or, more properly, confidence. Finding you can put the right notes over just one tune brings that feeling of eventually being able to do anything. Which in time you will.

7) You've got to be fearless!
One person I taught wanted to learn but was held back by not wanting to look stupid. He was frightened to make a mistake and consequently never really moved forward. He always moved in safe grooves and played easy stuff he already knew. He wasn't adventurous.

It doesn't mean playing nonsense, of course, but you've got to be willing to leap into the unknown, throw caution to the wind and just go for it. You might get it all wrong but it doesn't matter. Who cares? You'll get better and better.

There's a lot of mythology around being able to improvise but, apart from the basic requirements, it just means hard work. You've got to know your chords and scales, phrasing, theory, and so on, before you can apply it.

Everything you do, everything you practice, goes into your brain and memory. If it's not in there you won't be able to play it. It's as simple as that. The more you go over and over stuff, try things out, learn the essentials, the more it'll show in your playing.

Someone once interviewed Joe Pass. The interviewer asked him to play various scales and Joe zoomed through every one of them all over the guitar. He knew them, literally, backwards, forwards and sideways, and that only comes from ceaseless practice, repetition, and application.

Of course it's possible to improvise with far less knowledge than that but the important thing is just to begin. That way you get experience and experience is the one thing no one can give you.