ProjectTemplate v0.3-5 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 less stable than the versions that have been released on CRAN and is usually a little out of sync with the documentation. That said, if you'd like to use the most recent version of ProjectTemplate and don't quite understand how to use R CMD INSTALL, you can also install the devtools package from CRAN and then type

install_github('ProjectTemplate', username = 'johnmyleswhite')

to install ProjectTemplate from source.