The project summary page you can find here.
#Install the package
library(devtools)
install_github('multilevelPSA', 'jbryer')
#Load the package
library(multilevelPSA)
#List the available functions
ls('package:multilevelPSA')
Or you can download these files directly from R:
download.file('http://multilevelpsa.r-forge.r-project.org/pisa/pisa.student.Rdata', 'pisa.student.Rdata')
download.file('http://multilevelpsa.r-forge.r-project.org/pisa/pisa.school.Rdata', 'pisa.school.Rdata')