Check out example codes for "how to put icons inside of an edittext android". It will help you in understanding the concepts better.

Code Example 1

<EditText
        android:id="@+id/email"
        android:drawableLeft="@drawable/ic_email_black_24dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="textEmailAddress"
        />

Learn ReactJs, React Native from akashmittal.com