Getting home to my manual, I see that the instruction actually starts on pg 53.
As Howard points out, Some mics might not have a signal that's strong enough to be plugged into the "INPUT" jack, but I haven't come across any. with the help of the knob next to the jacks you can adjust to the level of most input sources. Note that the nob ONLY works for this jack, if my understanding is accurate.
As I stated in your previous thread, I usually record Internal Mic + External mic or instrument. I Start by plugging my external source to "INPUT". Go to TRACK PARAMETER . Press button 2 "INPUT" above the sliders, and adjust the input level with the above mentioned knob. Then I press button 1, and while holding it down press button 2. At this stage you should see MIC+INPUT at the top of your display. Now press cursor right once, and then cursor down tilll you get to FADER to adjust the level for the Internal Mic. Cursor Right once more to check External Source level. Cursor left twice and then exit to the main screen. Press buttons 1+2, or 3+4, check levels, RECORD !!!! If the peaks are to high (Total Clip) re-adjust sliders and try again.
I hope this works. If I've missed something I'm sure somebody else will set me straight
This is just basic. One can use limiter settings etc, but I'll let somebody else sort that out.