How to go to edit mode?
Read this. Editing help text on Wikipedia.
Use sentence case for article names
Sentence case such as the above section header, not Title Case.
Use easily typed characters in article names
Avoid using special characters that are difficult to type such as "™" in article names. It is okay to use the same in the article body.
To link to external image file
External to the wiki that is. You just need to include the bare URL for the image file, such as the following image.