。
I came early so I could get a good seat.
Literal
Good seat [subject-が] can-be-taken [in-order-to-ように] early came.
~ように (purpose/hope) marks the goal here — slightly different from ために. ~ように pairs naturally when the verb in the goal clause is a potential or non-volitional form. Here 取れる (potential of 取る) pairs with ように, not ために. The choice signals 'so that I can…' rather than 'in order to…'