You can use the Mixer Panel in Universal Control. Take a look at section 4 of the user manual that will tell you what you need to know pertaining to controlling the Studio 1824 outside of a DAW directly.
If referring to Stand Alone abilities:
The Studio 1824 isn't designed for stand-alone operation. Studio 1824 does not support pass-through ( StandAlone Operation) monitoring while not connected to a computer, this effectively would be a feature request. However, it does seem to retain the UC mix in temporary memory. Once the unit is powered OFF/ON, then the memory resets until sync is re-established with UC on a computer. UC settings are saved locally on the computer.
We might suggest instead considering something along the lines of a Series III Rack Mixer or the 1602 USB or AR Series StudioLive Mixers if you need stand-alone functionality.