I started with a White's years ago also, and still use a DFX at times. The one thing above all with the Explorer is move SLOW, in fact just barely crawl when you can. The unit will find things at that speed that the others have missed. Listen for a "flute" sound. It is the "good target" sound in most cases. Hunt in digital to start with, that way you can compare the sound to the number which will give you a basic idea of what may be in the ground. My suggestion is dig ALL repeatable sounds high tone and low, that means a lot of digging but you will soon be able to recognize a nickel from a pull tab. Be more concerned with learing the machine, not so worried about finding trophy items, there will be plenty of time for that later. Leave the machine it it's factory settings to start with, but try hunting in Ferrous tones, myself along with others love that setting.
You don't need to crank the Sensitivity up! It is best at around 20 in auto, too much and it's like turning your high beams on in fog. Sometimes less is better. Stability is important in the learning mode.
Have fun, there are a lot of veterans here so ask questions if you need!