To cite predictNMB in publications use:

  Parsons et al., (2023). predictNMB: An R package to estimate if or
  when a clinical prediction model is worthwhile. Journal of Open
  Source Software, 8(84), 5328, https://doi.org/10.21105/joss.05328

A BibTeX entry for LaTeX users is

  @Article{,
    title = {predictNMB: An R package to estimate if or when a clinical prediction model is worthwhile},
    author = {Rex Parsons and Robin D Blythe and Adrian G Barnett and Susanna M Cramb and Steven M McPhail},
    journal = {Journal of Open Source Software},
    publisher = {The Open Journal},
    year = {2023},
    volume = {8},
    number = {84},
    pages = {5328},
    url = {https://doi.org/10.21105/joss.05328},
    doi = {10.21105/joss.05328},
  }