I have a LaTeX file called testglister2.tex in my directory ~/GlisterBook. How do I import it into TeX.SE as an MWE? I use emacs as my text editor and from there I can copy the file, but how do I paste it as an MWE?
There is no file upload but you can paste the text from your editor then mark as a code region.
Select the text in emacs (eg
M-w to copy the current region) then (assuming you are using an emacs with bindings to your operating system GUI) that will be on the system clipboard so you can paste it into a text box in the browser (typically with Ctrl-V) then while it is highlighted, you can type Ctrl-K which will indent the text by four spaces which is (one of the) markdown syntax to mark it as a code block with preserved white space and line ends.