You can install the Psi+ package using pacman, yaourt or build the package from sources.
pacman -U your_package_file
You have also to install all dependencies that are required by the Psi+ package.
You may install Psi+ from AUR as root:
yaourt -S psi-plus-svn
For this method you need a PKGBUILD file to build the package from source and the makepkg utility.
Create a directory for building Psi+. The build session may look like this:
cd ~ # change the current dir to $HOME mkdir psi-plus # create a new directory cd psi-plus # enter it wget http://psi-dev.googlecode.com/files/PKGBUILD # or manually put the PKGBUILD file in this directory instead makepkg -i -s # build the package, download all the dependences # and install as root automatically
You can run makepkg without any parameters.
Then your package file will be created in current directory (or in directory specified with PKGDEST variable in your /etc/makepkg.conf file). You also have to install all dependences manually with the pacman utility.
After building you can install your package using pacman -U package_file.pkg.tar.gz command as root.
NOTE: to save traffic don't delete the directory (~/psi-plus) and its content, next time you will run the makepkg utility it will download 'only a minimal' amount of data from the svn and git Psi+ source servers.