Disclaimer: I figured it out by myself with explanation of signals given here (thank you very much!): https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3206644156

Here is picture of CTC board:


Numbers in line below mean switches, numbers near track mean signals.
Switch markings:
N - Normal; R - reversed.

Signal markings:
R stands for "to the RIGHT" or EASTBOUND;
L stands for "to the LEFT" or WESTBOUND.

In the middle sets signal STOP for both directions.
When you put switch to a side, it sets:
direction of choice - GO or CAUTION considering the next signal (in some conditions it will stay STOP) [look for signals guide from Introduction for more info];
opposite direction - STOP (you don't want trains on one track to go into each other, right?).

After setting one switch and signal push a gray button below to code the command into system. You will hear a clicking noises resembling ye good old electro-mechanical systems)))

White bulbs show occupied tracks and diverting non-CTC switches.
Red bulbs show occupied switch block. You can't operate them in this state.

NB: most diverging non-CTC switches won't allow putting GO signal through main line. You have to reverse switch when the train is past signal or command them to pass the STOP signal. Both seem kinda weird to me (:

Switches on small spurs or yards are still controlled on the ground.



Here you can see 2 bulbs at second line showing diverting switches to the third line. Description will say: "Occupied block, 0 cars"

Here is a simle example for setting a way for a passenger train going west from Whittier to Alarka Jct:


Train stopped at Ela Station (see white bulb glowing?)
When train goes out of a block, signals will automatically reset to middle position. In the beginning signal 62 was green when train was at Whittier.

I hope this would be helpful ;)