Here are 3 free courses for you to work on to improve your coding skills. Pick the path that corresponds to your level.

Beginner

Intermediate

Advanced

Learn coding syntax to write your first program!
(USACO Bronze and Codeforces Div 2 A/B Curriculum)

If you can write simple programs (using tools like loops), learn algorithms and data structures.
(USACO Silver/Gold and Codeforces Div 2 B/C/D Curriculum)

Once you know all the standard algorithms and data structures, apply them to hard problems to score higher in programming competitions.
(USACO Platinum and Codeforces Div 2 D/E , Div 1 D curriculum)