The location of the TemplateText is defined by Option/TemplateFile, often the default "template.txt", but Look into Context page or use CdmlDisplay on a TestPage to get its value. See HowToAdmin/DisplayVariables.

If the template comes from a file (filename must have an extension, typically ".txt" or ".html") then you combine the URL from accessing the wiki and add the directory path and file name to directly access the file.

If the template comes from a page (no extension) then you just go to the page to look at the template.

Typically any CSS code is part of the TemplateText and shows early. This has advantages in the ProWiki framework for copying, adapting and avoiding redundancies (although in general it is preferred to put CSS separately).