First follow the steps to build RPiPlay and use sudo make install to install it.
When use the quick installer from Raspap and overwrite the repository with this one:
curl -sL https://install.raspap.com | bash -r Erik1000/raspapwebgui
Don't forget to change the wifi country or hostapd will fail and you won't be able to connect.
After that Raspap should run as normal execpt there's a new Airplay option.
To make this option work do the following:
create a script called kill_rpiplay.sh in /usr/local/ with the following content:
/bin/kill -SIGKILL $(pidof rpiplay)
and a second script called stop_rpiplay.sh also in /usr/local/ with the following content:
/bin/kill $(pidof rpiplay)
Use chmod +x to make the files executable.
Then use visudo to edit the sudoers file.
Add the following:
www-data ALL=(ALL) NOPASSWD:/usr/local/bin/rpiplay,/usr/local/kill_rpiplay.sh,/usr/local/stop_rpiplay.sh
Now everything should run.