With a new bike, the likeliest explanation for excessive chain noise is the indexing of the gears being a bit off. This is easily remedied by manipulating the barrel adjuster at the shifter. This is a round, barrel shaped piece of the shifter at the point where the cable exits the shifter. Clockwise turning of the adjuster results in lower cable tension and will cause the cage of the derailleur to move a bit laterally to the outside. This allows the chain to run more in line--and quieter-- with the proper rear cog. Counter clockwise rotation of the adjuster tightens the inner cable which will cause lateral movement of the derailleur cage to the inside. It is seldom necessary in an otherwise correctly set-up system to have to turn the adjuster more than 1-1½ rotations.
First thing I would attempt is keeping the chain on the middle front chainwheel and shift through the rear gears as you pedal. I feel you'll be fine to be riding the bike, but you can certainly put the bike in a stand or suspend the rear wheel off the ground by hanging it from something sturdy like a tree branch. Just slip knot the seat post with a rope and get the rear end off the ground a bit. Placing the bike upside down has too many complicating issues and should be avoided.
So run through the rear gears and note whether the derailleur moves the chain to the next cog. Note the sound of the chain running on the cog. If a shift isn't made after a complete lever throw, shift back down, turn the barrel adjuster CCW a full rotation and attempt the shift again. Repeat if the shift is again unsuccessful. If you've turned the adjuster three rotations or more--or you've run out of adjuster threads, the cable will have to be tensioned at the derailleur pinch bolt. Because it's a new bike from a bike shop, it's best to take it back to them for adjustment if more than turning the barrel adjuster is required to achieve perfect shifting.
If excess noise is encountered in a gear--like the chain rubs on one of the neighboring cogs--position yourself behind the bike and take note of the alignment of the derailleur's upper, guide pulley wheel and the cog the chain is running on. The guide pulley should be directly underneath the cassette cog. Manipulate the barrel adjuster to achieve this alignment. If u see the chain is rubbing on the next smaller cog after a shift, loosen the barrell adjuster so the guide pulley moves more inside and makes the chain run cleanly on the proper cog. If the chain rubs the next larger cog after a shift, clockwise rotation of the adjuster will move things outside in line with the correct cog, silencing the excess noise.
Keep in mind that adjustment of cable tension via the barrell adjuster will be necessary in the coming weeks of riding as the cable stretches slightly during use. Again the bike shop will offer a free tune up after you've riidden the bike for a short time. Utilize this service.
