If, after setting Myster's download directories with the initial setup module you wish to change your download directory paths simply open the download preferences and double click a file type. You will be presented with a box like the one shown on the right. For example, if you have an MP3 folder and within this folder you've sorted your music into sub folders, by setting your MP3 folder as your Myster MP3 downloads location all these folders will be searched when making the files available online. Don't bother filling out a name in the Save As field. Myster ignores this information.
All platforms have different standard for save boxes.
This is the Mac OS X standard. Look at all that wasted space. Also, it will make Myster unnecessarily slow as it indexes all these files in the background. Set the directory as you would save a file, that is, set the directory as if you were going to save a file in it. It's as if you're saving one of your downloaded files.