How do I use the ticker for emails on a Mac?

It depends on the email program you are using.

For Mac Mail: create the HTML signature file and save it to your desktop, then you can drag the image in each time you send an email. There are detailed instructions for Mac mail here.

For Thunderbird it is the same on Mac as it is for the PC. There are instructions here for any Mozilla based email program. If you haven't come across Thunderbird before it is an excellent free email program, that is very easy to use and has great built in Junk mail filters. You can read more about it here.

For Entourage, the instructions are here.