:Well, 80.177.4.109 (Demon Internet customer), the first thing you should do is consider whether you will be able to cite reliable sources in support of whatever thesis you wish to advance. If your proposition is in any way speculative, or involves original research, forget it. Encyclopaedias are not the place for such material. In the case of Lindsay Anderson, it does seem a little far-fetched. Anderson was educated at Cheltenham College, and the movie if.... was shot at Cheltenham and Uppingham School.  

 :Let's say you have decided your sources are unimpeachable. Your first move would be to register as a wikipedia editor. This is a very simple process, starting on the very top line of the home page. You would then need to create a new section, headed, say, Portrayals of Tonbridge in fiction. It should probably go to the very end of the article. Go to the section "Notable Old Tonbridgians" and click on the edit link. Add your section title, preceded and followed by ==, then your text, which should not be overly discursive. When you cite your impeccable sources, do so within  tags. Good luck. Be brief.