INSTEAD is already in aur, so you can just compile and install it using the (in terminal as root):

$ yaourt -S instead

Or just download PKGBUILD from http://aur.archlinux.org and run:

$ makepkg -s

The finished package in this case is set as follows:

$ sudo pacman -U <builded_package_name>

Also in aur you may find INSTEAD-launcher.