。
The post office is a little off the main street.
Literal
Post-office [topic-は] main-street-from a-little be-separated-[past-た] place [at-に] exist-[polite-ます].
The structure X-から...離れたところ ('a place separated from X [by some distance]') is a common way to describe offset locations. 離れる ('to be separated, apart from') is intransitive; here its past-tense relative form 離れた ('separated') modifies ところ ('place'). 大通り ('main street, avenue') is the standard word for a major road.