how do you bind groups of units to a key?

[GeneralNoob9]

title
like when i play ophelia
say i have ophelia and 3 creeps

how do i bind that to a key to control all 4 at the same time

i highlighted all the units and pressed Ctrl + 3 and it didn't work for me

[[E]Clytemnestra]

you select them with mouse
you press ctrl+3 or whatever
when you want to select them you press 3 and it will select them(considering you don't have them already selected)

[[RawR]GrosFif]

^
Waht he said, works pretty much like in SC or WC3.