Front deraileur not shifting to lowest gear. (New bike)
Yes you can, no you should not.
Since it is a new bike assembled by the shop, I strongly recommend you let them fix it. And it must be for free (more correct: you already paid for it, they did not delivery an adequate service).
You are inexperienced. There is a very slim chance the derailleur is defective (for example the chain guides are weirdly bent after a transport accident), a very large chance you do not notice it (if it is the case), almost certain the shop will void the warranty by your tinkering on it (they already demostrated their sloppiness in giving you a bicycle not properly assembled).
If you are ready to take this risk, the defect you describe may be due to the L(ow)-H(igh) screws position.
You should be able to see them on the derailleur, hopefully they are labelled somehow. These screws are giving the boundaries to the derailleur movements.
It is annoying because you have to release the cable, set the L limit so the derailleur sits a bit closer to the frame, hence guiding the chain to the lower cog.
Try to pose the same questions on notorious internet page for searching images videos and you will find plenty of walkthrough.
What can go wrong? worst case, the front derailleur will not move, or the L-screw will come off, leaving the derailleur with no bound to the lower movement, with your chain falling in between the cogs and the frame: are you ready to push the bike to the shop or to a close-by bicycle mechanics?
Ps: thinking twice about your bike assembly, test your brakes, try to simulate an emergency braking action. The bad thing is that the shop may have been sloppy also in that aspect, the good thing is that all these things have always to be sorted out during the first rides, even when the bicycle is set-up by a highly regarded professional.