Are you trying to set the annotation scale to 1/4"=1'-0" ?
Or are you trying to set the viewport scale to 1/4"=1'-0" ?
If the first you can simply use the drop down toggle on the task bar.
If you are trying to set the viewport scale, simply click inside the active viewport and
on the command line : ZOOM > CENTER < 1/48XP
You can also select the viewport and use the annotation scale dropdown toggle on the task bar and select 1/4"=1'-0".