Collimating with a home-made collimation cap
The Gary Seronik website that you cite is a good one - it's not leading you astray!

There are a couple of important things to look at:


Look straight down the main tube of your telescope at the primary (largest) mirror. Is there a small paper ring or another mark dead in the centre of that mirror? If so, good. If not, read through this webpage http://garyseronik.com/centre-dotting-your-scopes-primary-mirror/
What are the lighting conditions when you're performing this? The photo you included is helpful but seems to imply that you might be pointing the scope at a bright light. This will wash out all contrast and make the procedure difficult. I collimate my scope just using ambient light during the daytime


Don't worry about only having one support rather than four. The key will be to identify your centre dot (you can just see it on Seronik's webpage, first picture ) and to see how it is centred when you look through the collimation cap onto the secondary.

Maybe read this article: http://www.skyandtelescope.com/astronomy-resources/how-to-align-your-newtonian-reflector-telescope/

Or search for Newtonian Collimation on Youtube?