[If I can observe something occurring and I have a reasonable explanation for it, arising from logic, common sense and past conclusions, is it true?]
Wait that didn’t make sense.
If I have a conclusion in mind, can I use the fact that my conclusion is observable as a supporting argument that my conclusion is correct?
I would say, no, the fact alone that it is observable doesn’t give more weigth to the conclusion. A lot of people seem to believe conclusions that are observable, but the conclusions are sometimes contrary to the observation. Actual verification is needed, i’d think.
I think the observation would have to arrive at a conclusion for you to verify it, otherwise it’d just be an assumption - and that concludes my conclusion on the matter! 
It depends on details of definition: if you mean ‘absolutely correct’ - if your conclusion were logically necessary - you don’t need supporting arguments. If you mean “correct” in a balance-of-evidence sense and hold that truth is arrived at by consensus, then go for it.
Popper: No, but you can use the fact that a conclusion doesn’t match observations as an argument that the conclusion is false.
Hume: Observation is just observation; you probably will use the observed facts to justify your conclusions, but there’s no logic behind it, just habit.
Kuhn: There are a vast number of conclusions that can be drawn from any set of observations. If yours fits best, we’ll go with that until we have more observations and a conclusion with a better fit.