Now that you have created a new cubical map you can assign HDRI light sources to any of its six positions. We'll assign a main light source and a fill light source to this cubical map.
To begin, select My Cubical Map in the Navigation Tree by clicking on it once. The Details Panel and Selections Panel are automatically updated to reflect information pertaining to the selected cubical map. Since no assignments have been made at this point, the top position is loaded automatically and the default thumbnail is displayed in the Details Panel (figure 1). Whenever a position on a cubical map has no HDRI file assigned to it the default thumbnail will be displayed in the Details Panel. At export time a blacked out HDRI file will be assigned to those positions in order to complete the cubical map.
figure 1 - Details Panel / Selections Panel
The fill light source will be assigned to the top position, so we'll start here. If the top position is not already selected under the View section of the Selections Panel as shown above, select it now. Whenever your cursor is over a button on the Selections Panel you'll see a callout in the upper right side of that section. This callout displays the name of each possible selection (figure 2).
figure 2 - Selection Callout
We'll assign a single rectangular softbox with a warm tone to the top of our cubical map to act as a fill light source. To do so, select the Rectangular Softbox button under the Style section. Select the Single button under the Configuration section. And finally select the Warm option under the Tone section. As you make selections their corresponding fields will be updated in the Details Panel. Once a selection has been made under each section the thumbnail will update to reflect the appropriate HDRI file. By default, the Exposure Value Offset is set to -0 EV. Since this light source is going to serve as a fill we'll set this value to -2 EV. The thumbnail will update again to reflect this change (figure 3).
figure 3 - Top Position Selections
To finish the assignments select the Front position from the Selections Panel and assign a Rectangular Softbox Style with a Double Horizontal Configuration and a Neutral Tone. Leave the Exposure Value Offset at -0 EV. You now have a complete cubical map ready for export (figure 4).