The Bleeding Edge forums are located on the main site: bleedingedge.com
Players are required to sign into the official website with their Microsoft account details, from here they are prompted to fill out the sign-up survey.
Once you have signed up for the technical alpha you will be able to access the Forums, some forum content can only be accessed if you receive an email from Ninja Theory confirming you have access to the technical alpha.
Once you have signed up to the technical alpha and completed the sign-up survey you have access to the Bleeding Edge Forums