I would recommend to have a look at the "Using_Your_StudioLive_Mixer_as_an_Audio_Interface_with_Universal_Control_V2_EN_25032019" manual, which you can find on the download page of your mixer. The basic things are descibed in section 3.3 "Apple Logic Pro/Express 7+".
Sections 4.1.3 "Digital Returns" and 4.1.4 "Main Digital Return" might also be of interest. By default, tracks are routed 1:1 to the channels. The Main L/R output of a DAW is supposed to be routed to USB streams 16+17 (37+38 for the 32-channel mixers), which is "Tape In" (Digital Return) in the mixer and UC Surface. Input source of Tape In needs to be set USB. This sends the Logic mix to the Main bus of the mixer and you can listen to the signal via headphones.
Be aware of possible feedback, when you route signals. Listening to the DAW signal will show some latency, even if there is no processing going on.