Roughly:
- use the outer knob on the MFD to switch to the system config page
- click the button on the MFD knob to enter focus into the first field in the screen
- use the outer knob (IIRC) to select the runway minimum length field (defaulting to 3000 feet)
- use the knobs to set the desired new minimum (2000 or 2500, say) - note this’ll be digit by digit, not a shorter/longer roll of the knob.
- click the button again to leave focus
Now the nearest menu should show the airports with shorter runways. I’m not sure if this is retained over sessions, or if you have to set it each time.
Frequency info should appear in the detail view on the MFD, again you’ll want to select the appropriate page with the MFD’s knob first.
For more detailed help, I recommend checking out Working Title’s discord chat – there’s a lot of folks who can help out with confusing bits of the interface.
You can find the links from the main G1000 NXi thread: