Go to www.twitter.com and sign in to your account. You will see a delete button near each tweet you sent. If you're using thirdparty apps, browser extensions or add-ons to tweet, you may have to hunt for the delete option. However, no matter where you tweet from, you can delete it easily from twitter.com. 

Delete account Head to www.twitter.com/settings/account and sign in to your account. Scroll to the bottom and click on 'deactivate my account'. On the page that opens, click on the deactivate button. Twitter first disables your account for 30 days. If you login to your account within 30 days, the account will be reactivated.