[Imp]

Can you be a bit clearer
I am going to assume by on the left you mean in the HQ screen.
Load scenerio
Buy units
Go to deploy if you cannot see them for some reason in the top left or right corner go into HQ screen & select the first or last new unit you bought.
It is now selected so place it on the map.
Probably easiest to line up new units in platoons/co then place them.
You can use N&P plus find function.
Remember to save it if forget it will be in slot 999