If you have activated the Authentication add-on (included in the Advanced plan), you have the option to allow your users to log into the native iOS and Android app with their Twitter account.
If you have a Twitter section, it means that you have already created your Twitter application.
In the left side menu, please go to Users > My Users > Settings > Connection/Subscription, and under "External Services" turn the "Authorize Twitter connection" button to ON.
From there, simply paste the Consumer Key and Consumer Secret in the appropriate fields.
If you don't have a Twitter application yet, follow the instructions given in this online help to create it and get your Consumer Key and Consumer Secret to fill in in the menu Users > My Users > Settings > Connection/Subscription.
Note: To set up the login via Twitter, the Access Token and Secret Access Token are not necessary, so you can stop at the first step of paragraph 4 of the Twitter online help.