The package can be installed directly from CRAN like this:
install.packages(rYoutheria)
Alternatively you can install the most recent development version of the package like this:
# install.packages("devtools")
# NOTE: If you have not installed devtools before you will need to restart you R
# session before installing to avoid problems
library(devtools)
install_github("rYoutheria", username = "BiologicalRecordsCentre")
library(rYoutheria)
A tutorial, included in the installation, can be found by following this link
If you have difficulties installing rYoutheria using this method try updating your version of R to the most up-to-date version available. If you still have problems please contact us or use the issues page.