How to add a license plate watermark or text watermark on Douyin:

Open the Douyin app and log in to your account.

On the Douyin homepage, click the plus button in the lower right corner to enter the video shooting interface.

At the bottom of the shooting interface, find and click the "Filter/Beautification" button at the top of the screen to enter the editing interface.

In the editing interface, you can choose filters, music, special effects, etc. At the top of this interface, there is a "Text" button, click it.

In the text editing interface, you can enter the text you want to display on the video, including the license plate number.

After entering the text, you can adjust the position, color, size and style of the text to suit your needs.

After completing the text editing, click the confirmation button in the upper right corner to add the text to the video.

Continue making other edits or adjustments, then click Next to complete your video editing.

On the video publishing interface, you can select the publishing scope of the video, add a description, etc., and then click the publish button to publish the video with the license plate watermark to Douyin.

Please note that adding license plate watermarks or text watermarks needs to comply with local laws and regulations, and respect the privacy and rights of others. Make sure you have legal permission to use your license plate number and follow TikTok's usage rules and community guidelines.