。
She explained her idea by means of a drawing.
Literal
She [topic-は] her own idea [object-を] picture [by means of-によって] explained.
~によって ('by means of, via') is the formal/written instrumental — a more elevated and explicit equivalent of plain で. Common in academic, journalistic, or formal contexts: 写真によって ('through photographs'), 議論によって ('through discussion'), 絵によって ('through a drawing'). 自分の考え ('her own idea, her own thinking') uses 考え as the noun form of 考える.