How to install captcha for pixelpost suffocate template

[Loupierrot]

Hello everybody,
I searched in all forums, but did not find the how to do this, so I post my question here.
I have an everyday and continuous spam on my photoblog with suffocate template.
Does anybody know how to install a captcha so the visitor has to write a series of numbers before sending any comment ?
If you know how to do this, is it possible to explain how do do this, the simplest way because I'm not very experienced.
Thanks a lot in advance for your precious help, dear pixelpost users ;-)
Here is the adress of my photoblog : http://www.aufildesjours.info
Pierre

[Dennis+]

did you fix it? did you read the instructions? is it working?

[Loupierrot]

Yes thank you Dennis I fixed it. I wanted to delete the message, but could not.

[Dennis+]

Ok fixed...