Write out your specific cell analogy as a list. Each part of the cell should have an analogical representation with specific details. For example, if your analogy is that the cell is like a country, the nucleus is the government which is in charge of the rest of the cell. Mitochondria would be represented as power plants, which create energy. Keep going until you have an analogy for every part of the cell
Write a short story based on your list. This story can be short and simple, focusing on one small part of the cell, or more complex, focusing on multiple systems in the cell. An example of a story for your cell analogy is the cell membrane as the Immigration and Customs center. A foreign invader that does not have clearance to be in the cell could be rejected, and very mad about it, continuously trying to figure out ways to invade the cell.
Draw out your story. If you want to draw a simple cartoon, stick with cell shapes that are fairly simple. If you want to make your cartoon more complex, use buildings and other items that are more relative to the human environment for your story. Use speech and thought bubbles for communication throughout. Coloring the cartoon is optional but can be helpful, especially if you are using simple cell shapes.