First you are able to format your tutorial using BBCode, for the most part you can use all standard BBCode for bold, italics, underline, images, and links.
There is one new BBCode that was added, that one is [timg][/timg] It stands for tutorial image, you use it almost the same way as the img BBCode except you use just the filename for the image, instead of the URL of the image.
When you go to upload the tutorial it will ask for a zip folder, inside the zip folder should be a tutorial.txt file (formatted with BB code), along with any images you created for the tutorial. Just upload the zipped folder and it will do the rest.
You can download an Example zip folder, that has been formatted, and added to the tutorials page.
The Tutorial once added: Ace of Spades: Getting Started (http://umh.sandcrawler.net/index.php?page=tutorials&command=view&id=34)