Create
Individualy, begin writing the text for your assigned section(s) using a word processor, such as Microsoft Word. Remember that writing for the web is far different than writing for print. Write brief, concise, logically organized text that can be scanned quickly. Use lists wherever possible. In the next stage of the process, the text you create will be copied into a wiki, which will remove all formatting, so don't be concerned about fonts, bold, or layout yet. Plain text with no formatting is what you want at this stage of the process.
Also, spend some time gathering images to supplement the other content on each page. Be sure to save citation information for any images that you collect, as it will be very difficult to go back at a later date to try to determine where each image was taken from. If you are using a web resource such as Flicker, be sure to only use Creative Commons licensed images. Use only those images and video that will illustrate the ideas contained in the text of your site in a way that is consistent with the goals and appropriate for the intended audience of the web site. You can insert images into a Word document, but be aware that when it is time to build the website, the images and text will need to be separated into separate files to be re-created as html-based web pages.