Are you talking about making a jpeg into a material in the DTE (which I would like to do but haven't figured out how, so far can only use what came with Bryce) or apply that jpeg to an object? To apply a jpeg to an object, put a marble in one of the channels then on the right side under the picture is a button with a P, click it and this will change the source from a procedural to a picture. Click the button above the pic (directly above the P button) and load your jpeg. Then play with the different mapping modes.