What the heck is a phonetic component?
Basically, it's a way of knowing the Chinese reading of a Japanese word based on a visually similar radical.
ε―ε[γγΌγ] and ζΆι²θ»[γγγγΌγγγ] both have characters with ζΉ (γ»γ, γΌγ) even though they are different kanji:ε and ι², they still have the same reading!
That's no coincidence. In fact, for all of these characters:ζΉ (γ»γ, γΌγ) β θͺ, ε, η΄‘, ι², 妨, ζΏ, θ¬, ε, θ³, θ¨ͺ, ζΎ, they have the same reading when used in their OnYomi.
For more info read this article: Read this great article: How to Look Up Kanji You Don't Know by Tofugu.
Instructions can be found link