Read thoroughly the help file through, it is very clear once you know what it is about!
Seriously now, the method is the following:
-Open SHPed.exe
-Button bottom-left, open WinSPMBT palette (WinSPMBT\Game Data\Graphics\WinSPMBT_Palette.pal)
-Button top-left, open the iconXXXX.shp file you wish to modify (all in the same folder as the palette above, refer to WinSPMBT\Game Data\Design\WinSPMBT_MasterIconList.txt to know which icon is in which file).
-Button bottom-center, open the icon collage to find the icon you are looking for.
-Change the icon number accordingly in the small number window (type or select with arrows). Careful: SHPed starts with icon #1 which is the SPMBT logo buffer, so you will always have a difference of 2 between the icon number in SHPed and in the list.
-Extract the selected .shp icon to Bitmap file (top middle button, arrow going DOWN to drive).
-Fiddle with the Bitmap icon as much as you want, using whichever image editor you are accustomed to (from MS paint to Photoshop), make sure to keep it the same size (89x89 pixels, 108x108 for larger units e.g. some aircraft)
-Be careful not to change the background color of the image, since it is the default transparent color for the game. You don't want your new units to hang around in the middle of a large white square!
***If you have followed these steps so far, you are now ready to import your modified Bitmap icon(s) into the .shp file:
Prerequisites: SHPed running, right palette selected, right shp open.
-Select the number of the icon you want to replace with you modified one
-Open the SPfix module (bottom right) and click 'show'. An image of the original icon will appear with a blue crosshair on it and columns of figures. Both indicate the centerpoint of this icon as used in the game. You'll use that later, leave it untouched for now.
-In SHPed main window, press the 'import bmp image' button (top-center) and select your modified Bitmap icon.
-Press the next button to the right, 'convert to shp'. If you had a shp icon or collage displayed (blue background), the display will now show your new icon.
-Not done yet! Now press the second last button on the top-right to replace the old icon in the file with your imported one. Make sure the icon number is correct!
-Modified .shp files are
always saved as Bignew.shp in the same folder as the original .shp. Now open Bignew.shp with SHPed.
-The new Bignew.shp file should show the content of the original iconXXXX.shp you have opened first, bar the first icon you have added.
-Now using the counter and collage, go back to this icon.
-Now back to SPfix: if you have left this window open and untouched, it should still show the header coordinates of the original icon. If your new icon is roughly the same as the original one, or at least has the same size, press 'write'. The crosshairs will be adjusted to your new icon.
-Using the small arrow tastes on the bottom and right edges, place the center of the crosshairs where you want your icon to be centered. This point will be displayed at the center of the hex in the game. Be careful for turreted units, both body and turret icons must have the same centerpoint, which will be the pivot of the turret.
Now repeat that procedure with all the icons you have to replace, then exit SHPed without bothering to save.
Your new shp file will be in the same folder as the original one and will
always be called "bignew.shp". So be sure to rename the new ones everytime you change files. Backup your original shp, then give its name to your freshly modified file.
Now you have it!
Hope that helps.
Cheers,
Plasma