If you want to say that you are simply in possession of something like,"I have a cat," you say, "Neko ga imasu." If you want to convey that you are currently "having" something or brought something, like, "I brought a pen," you can either say, "Pen ga arimasu," or, "Pen wo motteimasu." Imasu is for animate objects, arimasu is for inanimate. For intangible things you usually have to change the sentence around. So you wouldn't say,

Hi Recardo, I would like to add one more point. "Have" in English has many meanings and it is not only "to possess". http://dictionary.cambridge.org/dictionary/british/have So you need to use more accurate word to get the answer which exactly you want to know.

We have various translations for "to have" and many learners ask about this. Recently we answered the same question and I'd like you to take a look at this: http://www.italki.com/question/299575 If you have questions in our answers, please let me know. I'll try to explain. Espero que te ayude.