How can I group a few characters together like in an RTS game?

I have been following this excellent RTS tutorial series however, there isn’t any mention on how to group multiple of these independent characters into one group to form a unit.

The RTS tutorial series:

I would love to find some way to group a few of these guys together and make them into one unit similar to units in CIV game series.

Unfortunately, I am a huge noob with this stuff so I’m unsure of what to do in this situation. Any help would be greatly appreciated.

There are different ways you can do it with EQS, and AI.