Taken from notes written by David Mair AD7GH:

For one thing, we were mostly operating without setting up an active
QSO. There are standards for operating NBEMS and switching to the other
station (e.g. ending the message with k and a carriage return - whether
or not you include de <your callsign>).

You can enter a carriage return as-is with the enter key into the
message contents and acoid having messages concatenated with no space to
the end of the other station's message in the Rx view.

While the TX >| button at the right under the message entry window sends
a message and ends it with de <your callsign> k and a carriage return, I
suspect the intended usage isn't for every message to be ended that way.
The QSO button and the form at the top of the Rx window is probably
supposed to be used to switch from no contact to in a QSO and we need to
learn how to use it.

More deeply, the squelch settings for the Channel view, the Audio level
and the waterfall need to be learned to your own satisfaction to get
least noise comms. Unfortunately, each window has a different squelch
operation:

The Audio level squelch sets how high a level needs to be on the current
audio channel selection to show text in the Rx window. The audio level
itself is a little, dark green vertical bar that has a white background
and is at the second farthest right below the message entry window. The
farthest right is the squelch for it and sets the position the green bar
has to rise above for the decoder to be used on the current channel.

The Channel view squelch is immediately below the channel list and is a
horizontal bar and a number is shown to the left of it that is the
trigger level in dB. The lowest value is the most sensitive (i.e. -3.0
is more sensitive than 3.0).

The waterfall squelch is very helpful in seeing active stations in the
current received audio. Below the waterfall is a set of buttons and
fields. Leftmost of them is a button that changes between waterfall, FFT
and signal waveform view of the audio. When it is set to WF (waterfall),
immediately to the left of it are two fields. The first is the upper
signal level shown in the waterfall and the second is the lower signal
level. These should be adjusted with the left/right button either side
of each field and using the following logic.

When the waterfall is very noisy with blue content, adjusting the
rightmost of these to a lower number should reduce the noise. When the
display has nothing in it then adjusting this to a higher number should
allow moree to appear in the view.

When there is too much bright content (yellow, white, red) with no
pattern suggesting an active station then adjusting the leftmost of the
fields to a higher value will make the waterfall less sensitive. When it
has no bright content even when there is a station active (that you can
hear yourself) then adjust the leftmost field to a lower value.

A good default for off-air noise on a frequency is with the rightmost
control adjusted so that the waterfall is just on the black side of the
boundary where you start to see blue across the whole length (everything
you then see in any color is going to be above the level of normal
noise). In my own case I was using between -18 and -21 on the left field
and -40 on the right field.

Another thing that's important to figure out is selecting a channel. You
can click on one you see a text decode for in the Channel view but when
you are seeking an initial contact (at least for Team activities) the
best approach is to have the selected channel for initial work be 1kHz.
The selected channel is shown as a red horizontal bar under the
frequency offset axis at the top of the waterfall with two thin vertical
red lines going vertically down the waterfall, one at each end of the
bar on the frequency axis. The easiest way to do that is to click on the
waterfall as close as you can to the 1kHz point then use the tuning
controols in the buttons under the waterfall. There is a fairly wide
button for the waterfall speed that has options with the text "NORM",
"FAST", "PAUSE" and "SLOW". To the right of that button is the tuning
control for the active channel. The field has the centered frequency and
you are looking for it to be 1000. The double arrow buttons are 10Hz
steps and the single arrow buttons are 1Hz steps.