To install the CRAN version, use :
install.packages("JLPM")
To get the most recent update, install it from github :
# remotes::install_github("VivianePhilipps/JLPM")
install.packages("JLPM", repos = c('https://vivianephilipps.r-universe.dev', 'https://cloud.r-project.org'))
Some vignettes are available on the JLPM website https://VivianePhilipps.github.io/JLPM/.