Most sites then send you an email: you'll see "You're almost done - we have just sent you an activation email!" Click the link in the email. Your account is activated, and you're logged in.
Depending on the site:
If the email doesn't come, check your spam folder.
Click Login, enter your user name or email address and your password. Check remember me to stay logged in on this device.
After you log in, you're taken to your profile, or the page the site chooses.
On the login page, click Forgot Password?. Enter your email address or user name, and you'll get an email with a link to choose a new password.
If the site offers it, you can turn on 2 Factor Authentication in your Account Settings. After your password, you then enter a code sent to your email. Some sites require it.