I finally turned on the space heater in my apartment.
Today is the first day since last spring that I have had to use my heater.
ーI finally turned on the space heater in my apartment.
「アパートのヒーターをついに点けた」
to turn on the space heater で「ヒーターを点ける」
finally で「ついに」
ーToday is the first day since last spring that I have had to use my heater.
「春以降初めてヒーターをつけた」
to use one's heater で「ヒーターを使う・点ける」
since last spring で「春以降」
ご参考まで！
カナダ 
