ProjectTemplate v0.3-3 is currently on CRAN and can be installed using a simple call to install.packages()
:
install.packages('ProjectTemplate')
If you would like take advantage of changes to this package that are not available in the version on CRAN, please download the contents of the GitHub repository and then run,
R CMD INSTALL ProjectTemplate_*.tar.gz
For inexperienced users, running the bleeding edge version of ProjectTemplate is probably a mistake. It is generally much less stable than the versions that have been released on CRAN and is usually out of sync with the documentation.