This module is currently at "1.0" status. It should go into a "idealpaymentgateway" directory in your LemonStand modules directory.
You will need to generate a self-signed private key and certificate (unless you already have them). Use the following commands to do so:
Please note that these have changed for iDEAL v. 3.3.1!
/usr/bin/env openssl genrsa -aes128 -out priv.pem -passout pass:privateKeyPass 2048 /usr/bin/env openssl req -x509 -new -key priv.pem -passin pass:privateKeyPass -days 1825 -out cert.cer
In the module settings, you can either provide the path to the file or copy and paste the values. If you're on OS X, use:
cat filename | pbcopy to copy a file's contents to the clipboard.