This guide will show you how to promote a particular tweet on Twitter by placing it at the top of your profile page.
Sign in to Twitter and select the tweet you'd like to pin. Click on the Menu button (ellipsis button located below the selected tweet) and select Pin to your profile page:
The selected tweet will be displayed permanently at the top of your profile page.
N.B. This feature is also available for the Twitter mobile app (Android and iOS). Open the Twitter app and select the desired tweet. Tap on Menu > Pin to your profile.