A few questions after my first play

[stanfc]

I have been sick for awhile and have been having memory problems. I can't seem to to find how to attack another unit except with melee. I can't seem to get my unit to fire at another unit. What do I need to have my units fire against other enemy units? I looked in the getting started and help files and did not see how to fire my units against another unit.  Any help would be appreciated, losing your memory is a very tough problem.  Thanks