iRacing is a popular online racing simulator. Memberships are usually very pricey (>$100 AUD yearly).
Motorsport Australia is the national FIA ASN, but offers an iRacing code with completely free memberships (unlike other countries where you need to be a paying member - see Motorsports UK)
You must first sign up as a (free) Motorsport Australia member here. I didn't have to go through the Motorsport Australia membership hoop at the time, so can't comment on that step. EDIT: After you have your Motorsport membership number, you can complete the iRacing code request form (the deal link). After completing the iRacing request form, it took about a week for me to receive an email from Motorsports Australia with the iRacing code.
I did this a little while ago, tried it and didn't like sim racing enough to continue. Plus the pricing system is a bit crazy to me, but likely worth it for those who are competitive and love the online racing. Forgot to post it until I saw this Assetto Corsa deal which reminded me of iRacing lol.
The membership also includes the FIA F4 car in iRacing (from my experience, though not listed by Motorsport Australia - makes sense since these yearly codes are an FIA and iRacing partnership).
Nice reminder. Thanks.
I signed up Motorsport Australia membership a couple of months back, and never received my iRacing voucher. I have just emailed them to remind them about it.