How to use こと is correct.
But example sentence(?) is not correct.
いっしに→ひっしに hisshini
こなたのことを→あなたのことを anatanokotowo
みつけよう。 is correct.
Your sentence is not unnatural.
Japanese people understand this meaning.
This words is very romantic!!
If you say this words for Japanese, they might throb^_^
Does that make sense.
Sorry...I'm not good at English(*_*)