To the best of my knowledge, this is how ground forces training currently works.
In order to receive training the units must be on a colony surface, they cannot be inside a PDC or ship.
Training rating used is the training rating of the assigned brigade HQ officer plus half the training rating of the assigned divisional HQ officer. Training rating of the officer assigned to the actual combat unit has no effect.
To add ground units in SM mode, go to the GU training tab, select the type of ground unit you want to add from the list at the bottom(It is required to have researched the unit type before this) and hit the "add units" button on the lower right. This displays a prompt to enter how many of the selected units to add to the colony.
Regarding your fuel issue, as far as I'm aware civilian ships do not use your fuel stockpiles, however newly constructed ships will fill their fuel tanks(only to 10% if the class is designated as a tanker) from the stockpile.