1. Keep writing everything as you are.
2. Go back when you have your outline (because that's essentially what you have) and expand it.
If 2 seems overly simplistic:
2:
a) Read a book that you really like.
b) Pick a scene that you like that does something similar to what you're trying to do (introduce the hero to his to-be girlfriend; climactic death struggle; introspective moment where the character studies his navel and contemplates the meaning of the word "pudding.")
c) Copy that scene out, word for word. As you're copying, -read- it. Try to understand what that author is doing, and why they're doing it--what the effect is on you as a reader and how the author got that effect.
d) Find the same type of scene by another author whose work you like, and do it again.
e) Do it again with another author, and another. They're all going to do the same thing differently. Figure out how each works on you as a reader.
f) Go back to the outlined scene you have, and figure out what you're trying to accomplish in your scene. Figure out how you can accomplish what you're trying to accomplish, given how other authors accomplish their similar things. Write it.
g) Repeat for another scene, and another.
h) Now sit down and write the whole thing out, using the outline (and deviating from it as things expand and the world and characters reveal themselves to you.)
i) Now read through it again and identify all that you did right and that you really like.
j) Do more of that in the parts you didn't like as much.
It's not the only way, and it might not be the "right" way, but it's A Way.
As you write more, you're naturally going to get better, so what looks great to you today is going to look awful in a year, and worse in ten... but you'll keep getting better as you keep working at it, as long as you -do- keep working at it. Keep reading, keep writing... you'll get there
G'luck!