To cite PAST in publications use:

  Thrash, Adam, Juliet D. Tang, Mason DeOrnellis, Daniel G. Peterson,
  and Marilyn L. Warburton. (2020). PAST: The Pathway Association
  Studies Tool to Infer Biological Meaning from GWAS Datasets Plants,
  9(1), 58. URL https://doi.org/10.3390/plants9010058.

A BibTeX entry for LaTeX users is

  @Article{,
    title = {PAST: The Pathway Association Studies Tool to Infer Biological Meaning from GWAS Datasets},
    author = {Adam Thrash and Juliet D. Tang and Mason DeOrnellis and Daniel G. Peterson and Marilyn L. Warburton},
    journal = {Plants},
    year = {2020},
    month = {Jan},
    volume = {9},
    number = {1},
    pages = {58},
    url = {https://doi.org/10.3390/plants9010058},
  }