Since I don’t have a windows computer at hand at the moment, I can’t log in from Steam and doublecheck what I’m going to say so I’m talking out of memory…
However, as I recall, you have to select and unselect some of the options from the **ePic** login screen and input your **Standard** ePic username and password.
Note that you must do that in the ePic login screen within Steam, not in Steam itself.
That way, you can log in Steam with one password and in ePic with another.