I assume you just have to pledge at patreon, then on your profile at fenoxo.com you click on the patreon banner/thingy to get your patreon account linked with the website.
That´s how it worked for me in the very least.
Then the backer builds should stand next to "play".
If not I assume you´ll have to wait until you get the first charge.
That´s usually by the end of the month.