To cite package ‘methylGSA’ in publications use:

  Ren, X., & Kuan, P. F. (2019). methylGSA: a Bioconductor package and
  Shiny app for DNA methylation data length bias adjustment in gene set
  testing. Bioinformatics, 35(11), 1958-1959,
  https://doi.org/10.1093/bioinformatics/bty892

A BibTeX entry for LaTeX users is

  @Article{,
    title = {methylGSA: a Bioconductor package and Shiny app for DNA 
         methylation data length bias adjustment in gene set testing},
    author = {Xu Ren and Pei Fen Kuan},
    year = {2019},
    journal = {Bioinformatics},
    doi = {10.1093/bioinformatics/bty892},
    volume = {35},
    number = {11},
    pages = {1958--1959},
  }