2
check admin/preferences user info settings..
check to see if allow new registrations is enabled..
2nd, u may have it set so that admin has to approve new registrations, it is best to change this to require activation by user or activate automatically..
basically if it's set to user activation, when a user applies and submits their details, an email will be sent to them with a validation key, they then have to click this link in the received email b4 they can use the site..
automatic activation registers them immediately, but using this method can cause some abuse from people applying with bots and spamming..
the default is activate by user, so if thats not working, it is likely you have not setup your mail settings correctly.. check that the mail settings are correct, try sending an email to yourself via the site, if u receive the email then it is working.. if not, then u know the mail setup is configured wrong..
your 2nd question, no u can't turn off the info what is required, altho required is a vague term, as users can leave those fields blank if they want.. only the email, username and password are actually required..