Just use the video number, which you can find at the end of the URL.

For example, let's say you have this Tiktok, of people panicking when the High Roller stopped for 90 minutes and tilted badly:

https://www.tiktok.com/@loveeemartha/video/7010548466619337990

You would take the number at the end and do this:

[tiktok]7010548466619337990[/tiktok]

And it would show this: