To reach this point, you should have just just connected your audio interface and all of your audio gear and instruments, and started the audio setup wizard as explained in this help article.
You should now be looking at Step 2 of the audio setup wizard. Click the Audio Input Device list box (pictured below with arrow).
You see the list box open, and you need to find the option for "Scarlett Solo USB" (pictured below with arrow). This is the option for your Focusrite Scarlett Solo audio interface. Click this option in the list to select it.
You will now see the JamKazam app test your audio interface settings for 5 seconds, and you will see "Test Results" reported on the right side of the screen (pictured below with arrow). You should see a reported latency value of approximately 11ms (i.e. 11 milliseconds, which is eleven one-thousandths of a second), which is what the Mac system is reporting back to the JamKazam app. Sometimes this reported value is fairly accurate, and other times a bit less so.
Next, click to open the Frame Size list box, and pick the 1ms frame size option (pictured below with arrow).
Once you have your settings configured as described above, we recommend that you verify with your own ears that the audio interface settings you have chosen are working well. To do this, put on the headphones connected to your audio interface and grab your instrument and/or mic. Play your instrument and/or sing - do what you're going to actually do musically - and listen to how the audio sounds in your headphones. You should hear the audio clearly, and it should sound very good/clean. You should not hear any bad audio artifacts - like crackling, snapping, dropouts, or other audio glitches.
If you can't hear anything at all, you have something set up wrong. First, try to click the Resync button. If you still cannot hear anything, check that your gain knobs are turned up on your audio inputs. Check that any on/off switches on your microphones or instruments are set to on. Check that your headphone volume knob is turned up. Generally fiddle with all of these kinds of things to make sure everything is connected properly, turned on, and turned up. You can also check that you don't have a microphone or instrument port set to "line" level.
Please note that you may only hear your audio in one headphone, not in stereo in both headphones, at this point in the setup wizard. Don't worry about this. We'll get this sorted out in Step 3 next.
Optional Step to Further Reduce/Optimize Audio Processing Latency
At the bottom of this article is a link to download the installer for this driver. If you download and then install this driver, be advised you'll likely need to open your Mac's system preferences and take an action to allow the Focusrite driver to finish installation. And then you'll need to let the Focusrite installer reboot your Mac. Once this has been done, go back to Account/Audio Gear in the JamKazam app and click Add New Gear to restart our audio interface wizard. Follow the same instructions as above in this help article to pick the Scarlett Solo in the Audio Input list box, and then update your Frame Size setting to 1ms. You will see your latency is now measuring at 4.58ms (pictured below with arrow).
Our loopback testing indicates your Scarlett will now be operating at 5ms of audio processing latency.
Moving Ahead to the Next Step in the Audio Setup Wizard
If your audio sounds clean and good, then you are done with Step 2 of the wizard. Please click the orange Next button (pictured below with arrow) to move forward to Step 3 of the wizard, and then click here for the Step 3 wizard help article instructions.