저는 당신을 사랑합니다 sounds awkward. To say "I love you" in Korean, a more accurate translation would be 사랑해요, simply a verb, from the verb stem 사랑하다 (to love). 

Instead, we'll use another example.

저 사과를 좋아해요 (나 사과를 좋아해)
저 means 'I', which is the subject.
사과 means 'apple', which is the object. 를 is the object marker.
좋아해요 means 'like' (from 좋다) which is the verb.
In translation, the sentence would be 'I like apples.'
However, if translated in literally form, it would be 'I apples like.'

You may also omitt the 를, because in Korean, often 를 is understood already. 

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I learned that in English the sentence structure is the following: Subject - Verb - Object. In Korean, it's Subject - Object - Verb.

So if I say I love you, would that mean I am saying I you love? Or
Yes, it would be "I+는/은...you+을/를....love" (with particles)
in Korean it would be :
저 는 딩당 신 을 사 랑 합 니 다?
It should be "저는 당신을 사랑합니다".
(you should keep "the word spacing" in mind when writing Korean sentences because we count "space" as a character)

I love you
= 저는 당신을 사랑합니다(formal and polite)
= 저는 당신을 사랑해요(informal and polite)
= 나는 널 사랑해(informal and not polite)


\^o^/