There are two parts to your question: How users authorize your software and how they discover it.
Authorization Process: Glass users subscribe to Glassware using OAuth 2.0. Specifically, by granting you the https://www.googleapis.com/auth/glass.timeline
scope, they provide your service permissions to read and write to their timeline.
You can see this flow described in API Usage Stories page in this sequence diagram:

Discovery: This has not yet ben announced.
Users need to be directed to the URL that initiates your OAuth 2.0 flow to authorize. How users will find that URL is something that hasn't been answered yet. Don't stress too much about this during the developer preview. Instead focus on the features of the Mirror API.