How I can use a seed? Where I must type this numbers?

steam/steamapps/common/Don't Starve Together/data/databundles/scripts/scripts/worldgen_main

Copy that file out of the zipped folder then open with any text editor.

You'll see this line:

--SEED = 1568654163 -- Force roads test level 3

Delete the "--" of the line and change the numbers to the seed you want to use.

After changing the file save and copy and paste it back into the original folder.

If a run is short enough you can also use rollback to reset the world to start of day 1 on the same seed and show world settings after in the video (this is faster for quick resets).