For my research project I'll explain 3 different ways of manipulating the fabric that I used in my project personally. For this example I'll show how I folded the sleeves of my dress so that so that the right side of the fabric pointed outwards.
The first and most common way is to first simulate your garment (spacebar) and then use you mouse to drag the fabric. Doing this is probably the fastest way but the results leave something to be desired. For instance this is the way I had created my sleeve cuffs originally but they would eventually fall back down while I was editing the rest of the garment and I would have to go back and drag the fabric back in place several times.
Tacking in Marvelous Designer is the real world equivalent to pinning in the real world. With this tool you first select it from the toolbar and then click somewhere on your garment to start the tack and somewhere else to finish it. Think of it as entering and exiting with a straight pin.
This is another method I tried but I was also not happy with the results. Tacking is a great way to see how something can look quickly or to make it look like a character is hold fabric, if you pick tack to avatar. This allows you to try many different silhouettes quickly without sewing, but is not optimal for the final project.
3. Fold Arrangement
The third technique is using the Fold Arrangement tool and is ultimately what I used for this sleeve cuff. The fold arrangement tool is a quick alternative to setting the angle of your sewed stitches manually with is found in the properties of your sewed line, its a slider from 0-360 is hard to adjust to exactly where you want. With this tool you rotate one of the two fabrics connected to a stitch and automatically sets the fold angle accordingly. After setting this how I like I was able to create the rest of my garment without my cuffs falling down. :)