Hi Jonathan,
It’s not possible to modify the Method sign in page. All of your Method users are required to sign in via https://signin.method.me.
Your user’s data is stored in the Users table however, their sign in information (Method ID & password) are stored in a Method database and are not accessible via this table. Your users can be linked to an entity from the user setup and your sales reps are assigned to an entity. Therefore, your users are linked to a sales rep as follows: User > Entity < SalesRep.
I hope this helps.
-Audisho