" Only I can see it" is the correct sentence This song called "Only the lonely" by Browns will help you understand how to use the word "only". Only The Lonely Only the lonely will understand why my head is bowed And only the lonely will feel the way that I'm feeling now Only the hearts that have felt the pain of love that has slipped away Will understand the song I sing and the words I say Only the hearts that have felt the pain of love that has slipped away Will understand the song I sing and the words I say [ From: http://www.elyrics.net/read/b/browns-lyrics/only-the-lonely-lyrics.html ]

Both correct, prefer "I can only see it" in this case.

Your question is not very clear. Are you thinking of the word "barely" ? e.g. I can barely see it/ I can barely see the horizon/I can barely see the hotel opposite due to the pollution etc. Or do you mean "I am the only one who can see it ?"

if only i knew :P

In theory "only" is placed next to the word to which it applies, preceding verbs, adjectives and adverbs and preceding or following nouns and pronouns: He had only six apples. (not more than six) He lent the car to me only. (not to anyone else) I believe only half of what he said. But in spoken English people usually put it before the verb, obtaining the required meaning by stressing the word to which the "only" applies. I think the right answer to your question is "I can only see it". (You can only see it and not touch or something else.)