Once Rack is installed and launched (see Installing), you will see an empty rack with a toolbar.
Add a module by right-clicking on an empty space on the rack. To connect Rack to an audio output on your computer, click Core and then click Audio Interface. You can move modules around the rack by clicking and dragging an empty space on the panel.
Select an audio driver and device from the dropdown menus on the Audio Interface.
Continue adding more modules, such as VCO-1 and VC Mixer from the Fundamental plugin. Connect a cable from the Sine output of the VCO to the input of the mixer by clicking and dragging from one of the ports.
Connect another cable from the mixer output to the first channel of the Audio Interface's "output" section, and another cable to the second channel. You can stack cables on output ports by dragging from an input to an output, or by Ctrl-clicking (Cmd-clicking on MacOS) from an output to an input.
Finally, turn up the Mixer's Ch 1 volume knob by clicking and dragging the knob upwards.
At this point, you are ready to learn the rest of the Fundamental modules to build your own unique patches. I personally recommend that you try to push them to their limits before moving on to other official or third-party plugins. They are more capable than they might appear, and learning how to use them effectively will prevent you from being overwhelmed by the hundreds of other modules.