The first step is to create a new alpha channel in your color image.

This is done by opening the Channel Palette with the Window > Channel menu item. Click the pop up icon at upper right of the palette and select New Channel...

In the window that opens, type in a name and leave everything else as it is.

Next, select the mask image, then Select>All from the main menu and do an Edit>Copy.

Again select the color image and with your new channel selected, Edit>Paste the mask into it, as shown.

If you now click the top "eye" icon you can see how your mask will look. As the red part of the image shows, everything but the text is masked.

Save this file as .PSD.

Load Bryce and with the Create Palette open, click on the Leo icon.

This opens the Pict Editor.

Click on the empty tan square next to the Leo image.

This loads a File Selector where you load your .PSD file.

When it's done loading, the Pict Editor should look something like this image.

Hit the check mark to exit the Pict Editor and again from the Materials Editor.

Back in the main Bryce window you'll now see a 2D square selected. This is a render of the 2D square rotated around to be "square" with the camera and the sun moved around to illuminate the front of the object.

Click here to download the zipped .PSD file (checked on Mac/PC 5.01 and 5.5c).

Hope this helps!