This tutorial has been made an official page on Generals World.

C&C Generals: Zero Hour: World Builder: Tutorials: How to Show Captions in Maps 

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You should have a basic understanding of scripting for this tutorial.

1) Create a new script that is to show a caption.
2) For the action, choose, Scripting\Briefing\Show military briefing caption.
3) For the String '???', type a name of the caption, like Caption #. (The # just being any number)
4) For the milliseconds, type the number of seconds you want plus 3 zeros at the end. But if you have this number to small the caption won't show up completely. The maximum amount of characters a line of text that can be shown is 92. So from 1-46 charters, choose about 5000 milliseconds & 47-92, choose 10000 milliseconds.
5) Repeat that step for all your captions that you want to be shown.
6) Now open up a Notepad.exe & type Caption 1, or whatever you named your first caption. Then under that, type the caption you want shown & enclose in in quotes. then under that, type, End So it should look like this:

Caption 1
"Welcome to my map!"
End

Note, if you forget an End or a quote, then this might cause the game to not load.

Do this for all the other captions in your map too.
7) Now save the document as Map.str in your map folder. (You map folder is located in My Document\Command & Conquer Generals (maybe Zero Hour)\Maps with the name of your map on it.
8) If you typed the name of the caption differently in the World Builder as you did in the Map.str file, then you'll see in the game MISSING: 'CAPTIONNAME' meaning that the map can't find that caption in the Map.str file.
9) You can also have the caption go on to a separate line. So if you have a caption longer then 92 characters, then just add \n to create a separate line. So creat a caption in the Map.str file like this:

Caption 1
"Welcome to my map! You’ll have lots of fun on it! But… Who will win? We shall soon find out!\nMuhahahahhahahahahaha!!!!!!"
End

Note, you can only have 4 lines show up or the game will crash. Also, the first line is bolded. The 3 after are not. So if you don't want the boldness to show up, put a \n at the beginning of the caption, but this does sacrifice a line.

Be sure to add 5000 milliseconds for each 46 characters you type.

You can go ahead & just type the caption in the briefing action in the World Builder, but then the MISSING will appear.

In a multiplayer map the Map.str file won't work for the other players! It'll come up right on your computer, but not on there's. They'll just see, MISSING: 'Caption 1' It's because you have the map in advance, they don't. Once they exit Zero Hour & replay the map, then the caption will come up right. To deal with this, Type put in the briefing action, the caption itself. So if you want the "Welcome to my map!" to show, type that in the briefing caption, & then in the Map.str file, type the caption this way:

Welcome to my map!
"Welcome to my map!"
End

This way, the players will at least see, MISSING: 'Welcome to my map!'. Because of this, avoid using multiple line captions. Since that MISSING comes up, limit your captions to 82 character instead. But this doesn't apply to just Generals. The captions come up right in the game.

Nice tutorial Me Myself and Pi.
I just wanted to add that sometimes when you first add captions to your map, they don't always show up. I've found that exiting the game, then restarting the game and reloading the map works to fix this. I thought that might help those that have followed your directions to the letter and still can't figure out why it's not working.

This tutorial has been made an official page on Generals World. Thanks for your contribution and permission, Me Myself and Pi!

http://www.cncgeneralsworld.com/generals/zerohour/worldbuilder/tutorials/how-to-show-captions-in-maps.aspx 

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