Visit the park you are writing about. Bring a sheet of paper and write down everything you think is important. Focus on the details; write down anything that stands out about your surroundings. Focus on your five senses, and write what you smell, hear, taste, touch and see.
Make an outline. An outline is a rough plan helping you determine how you want your essay to be shaped. For a five paragraph essay, you should narrow down three points you wish to focus on and describe. Use the five sense method again, to detail each of your three points. If you are unsure which three points to focus on, write an outline with all of your points, and then choose the best points from there.
Write the body of your essay. It's important to remember to show, rather then tell. You do not want to simply tell the reader what you saw; you want to use words to show them. If you are using mostly action verbs you are probably showing, whereas if you are using mostly linking verbs, you are probably telling. Use descriptive words centered on your five senses. Be specific and use the proper names of things. For example, if there is a band at the park playing music, do not simply say there was music playing, say what song.
Write your introduction and conclusion. An introduction should prepare the reader for what the essay will be about. A conclusion should summarize all of the points you made.
Edit your essay for spelling and grammatical errors. This is a good time to make sure you used action verbs and remembered to show rather than tell.