Power up while holding the Menu button in.
You should look into reading up on G3X/G3X Touch Installation Manual, Section 35 (touch) or Section 34 (non-touch). It's all described in detail there.
Yes, assuming you're looking at 190-01115-01_an, how to get in configuration is on page 35-2 (section 35.2).
Do I understand you don't have the complete manual?
If not, you can download from Garmin, at:
https://static.garmin.com/pumac/190-01115-01_an.pdf