ok, first, u get house upgrades when u clean, repair, and start fishing, & also working each day will help...until 1 day when u clean something, repair something, or work, it will say: More furniture available!
or it might say: Jerry's renovations are open and are offering house upgrades.
(it will cost $1000 simoleons) If u hav the offert and the money, go home, click on the phone, there will b options 2 use the phone lik: call some1, invite some1 over, buy somthing, keep going down until it will say upgrade house...click there and u upgrade and thats it!
PS: after u upgrade ur house will b bigger and if u open the door, u will find a little spot so u could garden...go 2 the town buy a watering can then fertilizer, then seeds...go home & plant it..
I Hope I helped!!!!