You accidentally put both of your feet through a single hole of your pants.
You accidentally put both of your legs through a single hole of your pants.
You accidentally put both of your feet through a single hole of your pants.は足首辺り、You accidentally put both of your legs through a single hole of your pants. は足全体が入っていることを伝えたい時に使えます。
I think you have to put one leg in the other leg of your pants.
この場合、次のような言い方ができますよ。
ーYou have both your legs in one leg of your pants.
「ズボンの足１つに足が2本入ってるよ」＝「片方のズボンの足に、足が2本入ってるよ」
ーI think you have to put one leg in the other leg of your pants.
「足一本を、ズボンのもう一本の足に入れないと」＝「片方の足を、ズボンのもう片方の方に入れないと」
ご参考まで！
日本 
カナダ 
