Setting the visible frame - Demexis/Starbound-ColorOptionsPicker GitHub Wiki
If the files are uploaded successfully, two images of your clothes should appear in the main window. The first is with the original colors as they are. The second is the colored version, taking into account the entries of the current dye.
Regarding the pose, the default is the first frame of the idle animation. The pose and frame number can be easily changed using the drop-down lists.
Here you can also change the gender and set the checkbox to display/hide the mannequin.
Small example: