can anyone teach me how to farm and harvest stuff and what i use all that stuff for

go to your house and buy one if u have to then u can plant berres in your yard and craft items in your house

its exactly like lucario said,go to your home under the main menu section and if you don't have a home buy one from the estate agency and then plant berries in outdoor plot and craft items in indoor!

Go to estate agency, buy hause with farm, after that you can farm, some berry are have the requitment to plant, if you are new, try plant with oran berry , oran berry can find in item market or in map

If you need a guide for farming.
Better go here -> [you must login to view links]
Most/All of the information that you need are in there.