First off Photopostdev.com has no relation to this site other than being a hack site owned by the developer.
Of course any access's here would not be good there.
I will say this. You sign in to the forum like you already have with Zendiver and your password. To get to the members url all over there are links stating go to members area
A HTTP authentication box will appear. You need to enter your Photopost license username and password. PLEASE PLEASE DO NOT COPY AND PASTE. Type it in manually as most likely if your copy and pasting your carrying over a stray character etc.