。
I went to the station to see a friend off.
Literal
Friend [object-を] see-off-[purpose-ため] station [to-に] go-[past-った]-[explanatory-んだ].
見送る ('to see off, send off, bid farewell') is a compound verb — 見 (see) + 送る (send) — used for farewells at stations or airports, a culturally important act in Japan. ためは formal purpose, and んだ gives the explanatory tone ('the reason is...'). A small scene of saying goodbye.