Wikipedia Editing Job

When asked to edit Wikipedia, new thoughts and questions arise in my mind. I feel compelled to say something important, something that adds new meaning and definition. However with this addition, is it acceptable to include opinionated statements since it is a "free-encyclopedia"? If not, how can I state in my own words or edit any topic without being bias? It seems impossible to write anything in "your own words" without having an agenda or a particular opinion or personal feeling being expressed.
Also, the particular page that I would edit is another decision that is difficult to make but I would choose the page based on my own knowledge. I am educated in many subjects as a college student, but particularly I would want to create a page about a significant place in my life or a topic. Perhaps I would chose to create a page about Paradise Bound Ministries, the organization that I traveled to Guatemala with.I could give the founder, church affiliation, and work accomplished by the organization. I could also create a page about South Haven High School on Wikipedia as a graduate. I could give a detailed account of a student's experience there and hope that other students would also edit the page to give it the most comprehensive and well represented account possible about the high school by including all of the school organizations, athletics, classes, and accomplishments.