Hi, and welcome!
Please see the FAQ: What's a reproducible example (`reprex`) and how do I do one? Using a reprex, complete with representative data will attract quicker and more answers. This question doesn't require it, though.
Packages like this one that are still in development can often be installed from github.
First install the devtools package
if(!"devtools" %in% rownames(installed.packages())) install.packages("devtools")
then
devtools::install_github("crsh/papaja@devel")