how to change twitter dp

You can change your profile picture or modify data on the profile tab in the settings.
You can also click Edit profile, which appears in your profile when you are logged on to this account.

Modify or delete your profile photo:

Please login to your account.
Click the gear icon in the top navigation bar and select Edit profile.
To do this, click the button change the photo next to your photo. Given the option, choose an existing photo, take a picture or delete your existing photo.
If an existing image in your computer, can your file up to 2 MB in one of the following formats: JPG, GIF, or PNG. (Twitter does not support GIF.)
After selecting the file, and click then click Save.
Here, you see a message that your image has been successfully published your profile.