Log in to your account on the web at twitter.com.
Click the more icon.
Select Settings and privacy from the drop-down menu.
Go to your Privacy and safety settings.
Click the Your Tweets section and check the box next to Mark media you Tweet as containing material that may be sensitive.
Note: When you have this setting enabled, people who visit your profile may see a message letting them know your account may include potentially sensitive content and asking them to confirm they still want to view it. People who have opted in to see possibly sensitive content will still see your account without the message.