。
She tried to put enthusiasm into her voice.
Literal
She [topic-は] her own voice [into-に] enthusiasm [object-を] put-in [tried to-ようとした].
~を込める ('to put X into, to pour X into') is the standard verb for infusing one thing with another — emotion into a voice, effort into work, love into food. Pairs with に for the receiver of what's poured in. ~ようとする ('to try to') wraps the action: she made a deliberate effort to inject enthusiasm — implying it didn't come naturally in this moment. Past ~ようとした gives a one-time past attempt.