Invalid Coupon Code

I’m spending far to long trying to set up this software every turn i make i find a new problem, so im going to ask for some help in setting up my site here: https://buywoodcrafts.com/

ive been looking around these forums for a long time now and im just getting more and more confused so ive taken the plunge in asking for any advise to help me.

1) every time i try and use a coupon code i get: “Invalid Coupon Code” despite having set it up and saved in Checkout Setup>Coupons Options

2) i have no home page so wordpress tells me but the page you land on when you go to my site is the home page so some widgets will not work because i can select pages for the widget to be displayed on but i cant select the home page because there isn’t one or a way i can select it.

3) i would love a flash banner on the home page that you land on when you go to the url.

TIA