Question

how can I study numerical methods

Answer 1

First, understand high level math:

(1) calculus

(2) differential equations

(3) infinite series

(4) statistics and probability

Next, take a bunch of computer science courses:

(1) basic programming language such as C++, Java, or Fortran

(2) several numerical methods classes

(3) computer design and digital circuits, so you understand the inner workings of computers

(4) at least one finite automata class so you understand process flow and the theory behind why programming languages work

(5) a couple of algorithm design and analysis classes

(6) engineering or physics courses with several computer projects where you have to model the real world. This gives you your initial practice.