You can do this from within your on-line account.
Go to the talktalk web page
and click on 'My Account' in the top right corner.
Using the login details sent to you by talktalk login to your account.
On the menu list on the left-hand side select 'Phone & broadband' then from the sub menu select 'Manage services.
To see who's calling you in Calling features tick the box for the 'Privacy Pack'
To go Ex-directory in 'Directory' listing select Special directory.
To have you number withheld go to Privacy features tick the box for 'Withhold Number'.
All these are free for talktalk customers.
It will probably tell you it will take about 24hrs for the change to be effective.
As for joining the talktalkmembers
forum it is very common for people to have difficulties joining. I recommend strongly that you persevere. Thing to try are the talktalkmembers contact page
or you can send one of the OCE talktalk staff a private message even if you're not a memeber and they will sort it out. You can even try sending a private message to the talktalk support
on this forum.
Hope this help you or anyone else having similar problems.