The LaTeX template is distributed as a ZIP archive, which you should download and unzip. Please start by reading README.txt, also copied as follows:

README.txt
Prepared by C. Pinon (cjpinon@implicature.xyz) for EISS 13 (see
https://implicature.xyz/eiss13/)
2020-12-30 v3.2a
2020-02-02 v3.2

This is a LaTeX template package for EISS 13, for either pdflatex or
latex as the typesetting engine.

This package consists of a main directory with four files and one
subdirectory eiss/ with 11 files:

README.txt
lppl.txt
EXAMPLE_master.pdf
check-for-packages.tex
eiss/
  eiss.sty
  eiss13_logo_blank.eps
  eiss13_logo_blank.pdf
  glossa.bst
  AUTHOR_master.tex
  AUTHOR_body.tex
  AUTHOR_refs.tex
  EXAMPLE_master.tex
  EXAMPLE_body.tex
  EXAMPLE_refs.tex
  EXAMPLE_bib.bib

You're reading README.txt. :-)

lppl.txt contains the package license (the LaTeX Project Public License
Version 1.3c).

EXAMPLE_master.pdf is an example illustrating eiss.sty,
AUTHOR_master.tex, AUTHOR_body.tex, AUTHOR_refs.tex, and the style
sheet. (You can try to compile EXAMPLE_master.tex in the subdirectory
eiss/.)

check-for-packages.tex is a file that you can latex in order to check
for packages explicitly required by eiss.sty. Just latex this file and
pay attention to the output (or examine the LOG file afterwards).

Turning to the subdirectory eiss/:

eiss.sty is the LaTeX style file for EISS 13. It may be easiest to keep
this file in the same directory as your TEX files (but you could also
put it somewhere else where LaTeX searches for files). Please don't
modify it.

eiss13_logo_blank.[eps|pdf] are two files containing a blank logo. One
of these files is inserted by AUTHOR_master.tex -- the file inserted
depends on whether pdflatex (then the PDF version) or latex + dvips
(then the EPS version) is used to compile AUTHOR_master.tex. It may be
easiest to keep these files in the same directory as your TEX files.

glossa.bst is a BibTeX style file from the journal Glossa. This is the
BibTeX style file that you should use. This file is also available at:

  https://github.com/guidovw/Glossalatex

(This file is included as a convenience. It's not clear what its license
is.)

AUTHOR_master.tex, AUTHOR_body.tex, AUTHOR_refs.tex -- these three files
are to be edited for your paper:

  - AUTHOR_master.tex is the file in which you set 12 parameters for
  your paper, as well as for loading any packages that you need. Please
  follow the instructions in it (it's intended to be
  self-explanatory). This is the file that you compile. It's advised to
  rename it (by replacing "AUTHOR" with your last name, e.g.,
  roussarie_master.tex).

  - AUTHOR_body.tex is the file for the body of your paper. This is
  where you should write your main text. It's also advised to rename
  this file (by replacing "AUTHOR" with your last name).

  - AUTHOR_refs.tex is the file that loads your BIB file. Please follow
  the instructions in it. Please also rename this file accordingly. (In
  the case of EXAMPLE_refs.tex, the BIB file loaded is EXAMPLE_bib.bib.)

EXAMPLE_master.tex, EXAMPLE_body.tex, EXAMPLE_refs.tex, EXAMPLE_bib.bib
-- these four files are the source files for EXAMPLE_master.pdf in the
main directory. You're encouraged to try to compile EXAMPLE_master.tex
as a way to test your system (in addition to running latex on
check-for-packages.tex in the main directory).

Before sending the source files for your paper to the editors, please
make certain that you've paid attention to the points mentioned at
https://implicature.xyz/eiss13/latex_bibtex_advice .

If you have any questions, please don't hesitate to ask. Happy LaTeXing!