You cannot delete your Twitter account from a mobile app. You must login to the Twitter site from a web browser. Follow the steps below.
Delete Twitter - Website - Slides & Instructions
Remember, Twitter collects everything from the content of a tweet to the time, time zone and type of device from which it was sent. And, Twitter can share any/all information collected with third parties.
Deleting Twitter? Share Your Experiences
Questions & Answers
Twitter doesn't immediately delete your account when you deactivate it. The site holds your data for a period of 30 days while it begins to remove your data from its systems.
Yes. After deletion twitter offers a 30 day grace period. During this time you're given a chance to reactivate your account if you'd rather not get rid of it. All you have to do is log back in. If it's past 30 days then the answer is no. Your data will be gone and you cannot reactivate.
No. If you deactivate your account and do not change your email then you will not be able to open up a new account with the same email address. You can, however, make your username or email address open for reuse before deactivating your account. To do this, you must first change the content in your profile and then confirm the change prior to deactivation.
Probably not. Twitter states that if you're deleting your account for the purpose of purging your tweets from a search engine, it may not work. Search engines index information and don't necessarily check back in to see if an account has been deleted.