I cant find the Data (D:) folder

Kinda lost when it comes to this.

It's not a folder; it's a hard drive. For you, it'd be whatever drive you installed Diablo 2 to.

Ugh I've been trying to do this for awhile with no success. I've uninstalled/reinstalled and tried again.

When I open the runes.txt file it opens in notepad, is Thai ok?

Yes it is a .txt file so no problems there.. you just have to create the folders like in the picture.

your diablo II folder (where is the game.exe) -> create the folders -> insert runes.txt there -> put the -commands to the shortcut or where ever you start the game
play the single player with ladder runewords

If after all these instructions you're unable to use ladder runewords, uninstall D2.

Then burn your computer.