明日私は忙しいです。だから、私の代理をする人を手配しました。

。、。

I'm busy tomorrow, so I've arranged for someone to fill in for me.

Literal

Tomorrow I [topic-は] busy-is. Therefore, my substitute [object-を] do person [object-を] arranged.

だから ('therefore') connects two sentences causally. 代理をする人 ('a person who acts as substitute') uses a relative clause. 手配しました ('arranged') is a Sino-Japanese suru-verb for making arrangements. The sentence demonstrates how Japanese handles multi-clause explanations.