How to become an Editorial board member? How to become an Editorial board member?Is it appropriate to contact journal's Editor in Chief to show interest for joining editorial board?
That's generally not a job you can apply for, but a job you're asked to take on. At least in reputable journals, the members of the editorial board are largely scientists well known in their field. They have that role because the editor-in-chief trusts their opinions and perspectives on submitted papers, and also because they have the stature in the field to write to potential reviewers and ask them to review a paper. Well established researchers also have fewer potential conflicts of interest: They no longer have promotions coming up, and so feel less conflicted about rejecting papers by people who might otherwise be asked to write letters of evaluation about their promotion.

I don't know what your career status is, but suspect that because you are asking the question that you are still young. As an editor-in-chief, I usually try to avoid using younger researchers as members of the editorial board. That's not necessarily because I don't trust their judgment, but because they have conflicts of interest and because they will have a harder time receiving the necessary reviews within a reasonable time frame.